Methods for improved power transmission performance and compositions therefor

ABSTRACT

Advanced methods are provided for achieving improved power transmission performance, and unique fluid compositions useful for practicing such methods are also presented. In particular a method and related composition is provided for reducing NVH in a power transmission apparatus having a friction torque transfer apparatus, such as, e.g., a shifting clutch, comprising maintaining a negative ∂μ/∂T slope, and/or a negative ∂μ/∂P slope, during engagement of the friction torque transfer apparatus.

This application claims the benefit of priority of U.S. ProvisionalApplication No. 60/695,183, filed on Jun. 30, 2006.

FIELD OF THE INVENTION

The present disclosure relates to methods for providing improved powertransmission performance and fluid compositions suitable for use inpower transmission applications.

BACKGROUND OF THE INVENTION

An automatic transmission in a vehicle generally includes a multipledisk clutch in which a plurality of friction plates, each having afriction material bonded to a surface of a metal substrate (core plate),and a plurality of separator plates, each constituted by a single plateor more, are arranged in an alternating sequence. In an automatictransmission lubricated with transmission fluid, these plates arefrictionally connected/disconnected to/from one another so that drivingforce is transmitted/released. Wet friction materials used intransmission clutches have included paper friction materials, carbonfiber friction materials, elastomeric friction materials, sinteredfriction metals, and so forth. The term “wet”, in this general context,refers to a friction material wetted with transmission fluid.

New and advanced transmission systems are being developed by theautomotive industry. These new systems often involve high-energyrequirements. Component protection technology must be developed to meetthe increasing energy requirements of these advanced systems.Commercially, it is known to add various additive packages to automatictransmission fluid, including, among other things, extreme pressureagents, antiwear agents, antioxidant systems, corrosion inhibitorsystems, metal deactivators, anti-rust agents, friction modifiers,dispersants, detergents, anti-foam agents, and/or viscosity indeximprovers. However, not all additives interact predictably or well withone another. The friction properties are particularly important inclutches that need more friction to transfer torque but less friction ingears, bearings and seals. As a lubricant in a transmission, the fluidused in the clutches is also in the gears. Reducing friction in thegears, bearings and seals increases the lives of these components andimproves fuel mileage, but reduces torque capacity of the clutch and theability to transmit power. When friction is reduced, higher clutchforces are needed to achieve sufficient torque capacity, which can leadto mechanical failures.

An important performance requirement for an automatic transmission fluidis the ability to prevent noise, vibration, and harshness, i.e., “NVH”for purposes herein, from occurring in the clutches of a transmission.Automotive power transmission fluids are being called upon to providespecific frictional properties under very demanding conditions oftemperature and pressure. For instance, multiple plate disk clutches areused extensively for shifting gears in automatic transmissions underhigh static and quasi-static friction conditions. During shifting, oneor more clutches is engaging or disengaging. In these active clutchesthe automatic transmission fluid and friction material experiencesubstantial changes in pressure, temperature, and sliding speed. Thefrictional interaction of the automatic transmission fluid and frictionmaterial is a function of these variables, so the coefficient offriction has tended to change during clutch engagement. Changes in afluid's frictional properties as a function of relative sliding speed,temperature, or pressure as a result of these conditions may lead toperformance degradation in the vehicle “feel” that is readilydiscernible to the vehicle operator and passengers. Such discernibleeffects may include shift chatter or squawk in the shifting clutches,shudder or vibration in slipping torque converter clutches, and/or harshshifts (“gear change shock”), collectively referred to as “NVH” herein.Frictional properties of a fluid ideally would be selected to suppressNVH in the clutches. Moreover, an automatic transmission fluid ideallywould reduce occurrence of NVH without compromising the frictionalproperties needed for good shifting performance. For instance, thestatic friction level is important in an automatic transmission wherethe clutch pack must have sufficient holding capacity to transmit powerfrom the engine to the wheels. In addition, conventional automatictransmission fluids can be highly susceptible to significant loss of thedesired frictional properties as they age, and an ideal fluid wouldaddress that consideration as well.

There is a need for transmission fluids that reduce NVH whilemaintaining high static and quasi-static friction, and/or which haveimproved anti-NVH durability upon aging, especially under conditions ofhigh temperatures and pressures. Such fluids would minimize equipmentand performance problems while maximizing the interval between fluidchanges. By enabling smooth engagement of torque converter and shiftingclutches, these fluids would minimize NVH, and in some cases improvefuel economy, over a longer fluid lifetime.

SUMMARY OF THE INVENTION

The present invention relates to the advanced methods for providingenhanced power transmission performance and unique fluid compositionsuseful for practicing such methods.

In one embodiment, a method is provided comprising appropriate selectionof a transmission fluid formulation for reducing NVH in a powertransmission apparatus having a friction torque transfer apparatus,comprising maintaining a negative ∂μ/∂T slope during engaging, slippingor modulating thereof, where “μ” represents coefficient of friction and“T” represents temperature. In one embodiment, the reduction obtained inNVH may be achieved in the form of a reduction of one or more of shiftchatter, shudder, vibrations and/or harshness relative to a referencefluid comprising a commercial ATF product. Under preselected conditions,this negative ∂μ/∂T slope has been found to be maintainable without lossof static and quasi-static friction properties of the friction torquetransfer apparatus during engaging, slipping or modulating thereof.

The discovery that providing and maintaining a negative ∂μ/∂T slopeduring engaging, slipping or modulating of a friction torque transferapparatus can reduce NVH is surprising and runs counter to theconventional theoretical thinking in the power transmission field. Thepresent investigators also have discovered that merely using atransmission fluid in the operation of a power transmission which yieldsa positive slope of coefficient of friction (μ) versus sliding velocity(v) is inadequate to significantly suppress and control NVH. It hassurprisingly been discovered that the transmission fluid run in thetransmission must possess a negative friction dependence on temperaturein the operation of the friction torque transfer mechanism of the powertransmission to suppress NVH in a meaningful manner. In one embodiment,this applies to prevention of NVH (e.g., chatter, squawk, shudder,and/or noise) during the engagement of a friction torque transfermechanism, such as a shifting clutch. It ensures a smooth shift in aclutch when plate temperature at the friction interface is rising duringengagement. Provision of negative ∂μ/∂T condition in a transmissionmakes it possible to raise the overall value of the coefficient offriction at essentially all or all sliding speeds and at the same timeprevent squawk, shudder and chatter from occurring in the clutches. Italso prevents lock-up when a limited amount of slipping is desired, asis often the case in a torque converter clutch or a limited slipdifferential clutch. The negative ∂μ/∂T condition is important informulating higher coefficient of friction and higher torque capacityfluids that will still suppress NVH. The significant improvements intorque capacity and NVH suppression may also make it possible fortransmissions which are smaller and/or operate at lower pressure, all ofwhich improve fuel economy. The discovered significance of the negative∂μ/∂T condition is not necessarily limited to any particular modalityfor providing this prescribed performance condition.

The above-indicated inventive methodology of providing negative ∂μ/∂Tcondition in a power transmission is applicable to friction torquetransfer apparatus in general, including, for example, a shiftingclutch, a starting clutch, a torque converter clutch, a band clutch,disk or plate clutch, a limited slip differential clutch, and so forth.The types of power transmission in which the inventive methodology maybe applied are not particularly limited, and include, e.g., automatictransmissions, manual transmissions, continuously variabletransmissions, and manual automatic transmissions, and so forth. Thesetransmissions may be used in a variety of applications such asautomotive, marine, aerospace, industrial, and so forth. In a particularembodiment, the inventive method is applied to a multi-speed automatictransmission, such as a 4-speed or more transmission. In one embodiment,it may be selected from the group consisting of a 5-speed automatictransmission, a 6-speed automatic transmission, and a 7-speed automatictransmission, and particularly 6-speed automatic transmissions. Thetransmission apparatus also may comprise a dual-clutch transmission or aheavy duty automatic transmission.

As indicated, in one embodiment, appropriate selection of a transmissionfluid formulation for lubricating a friction torque transfer apparatusduring operation of the transmission apparatus is responsible forproviding the condition of a negative ∂μ/∂T during engaging, slipping ormodulating of the friction torque transfer apparatus. That is, additiveand fluid compositions have been developed for transmissions to providehigh static and quasi-static friction properties while minimizing NVHcharacteristics. These compositions are also effective at providing thesame degree of NVH-suppression performance after aging of the fluid.

In one embodiment, a transmission fluid is provided in this respectwhich comprises alkoxylated amine, dihydrocarbyl phosphite, metallicdetergent, and phosphorylated succinimide. Properly balancedcombinations of these four particular components have been discovered tohave the unexpected combined effect of bringing about the negative ∂μ/∂Tslope condition during engaging, slipping or modulating of a frictiontorque transfer apparatus of a transmission apparatus, which conditionsurprisingly has been found to provide NVH suppression withoutquasi-static or static friction losses of significance. Indeed, it hasbeen observed that providing even relatively small negative ∂μ/∂T valuesyield very significant improvements in anti-NVH. Although highermagnitude negative ∂μ/∂T values also may provide some additionalincremental improvements in anti-NVH, the most significant gains in NVHsuppression generally can be attained at relatively small negative ∂μ/∂Tconditions. The respective amounts of these four components needed toattain the negative ∂μ/∂T slope condition generally are governed by theexperimental discovery and observation that the presence of alkoxylatedamine, dihydrocarbyl phosphite, and metallic detergent independentlyincrease the negative value of ∂μ/∂T, i.e., make it more negative, whilea decreasing level thereof has the opposite effect on ∂μ/∂T, i.e., makesit less negative (i.e., a negative value of smaller absolute magnitudeor a positive-value). On the other hand, increasing amounts of thephosphorylated succinimide component make ∂μ/∂T less negative, whiledecreasing amounts have the opposite effect. Levels of these fourcomponents should be balanced with above criteria in mind to introduce anegative ∂μ/∂T condition, particularly a small negative ∂μ/∂T conditionat all conditions over normal operating range for improving anti-NVHperformance, among other things. Lesser included combinations of thesefour components will not behave reliably in the above indicated manner.

In one particular embodiment, the transmission fluid compositioncomprises about 0.002 to about 0.5 wt % alkoxylated amine, about 0.001to about 0.5 wt % dihydrocarbyl phosphite, about 0.01 to about 1.0 wt %metallic detergent, and about 0.01 to about 12 wt % phosphorylatedsuccinimide. These components may be introduced into a fluid compositionpredominantly comprising a base oil as an additive concentrate orcomposition in amount of about 3 wt % to about 20 wt %, particularlyabout 5 wt % to about 15 wt %, based on the overall fluid composition.Nominally, the alkoxylated amine and dihydrocarbyl phosphite arefriction modifiers; the metallic detergent has detergent effects; andthe phosphorylated succinimide is an ashless dispersant; however, theircombination in effective amounts also has been found to bring about theabove-mentioned negative ∂μ/∂T slope condition during the engaging,slipping or modulating of a friction torque transfer apparatus of atransmission apparatus, which is associated with the prevention ofundesirable NVH phenomena at increasingly higher pressure thresholds,without quasi-static or static friction losses of significance. It alsowill be appreciated that the fluid composition can be provided as aconcentrate, which may be blended with a major amount of base oil toform a more dilute composition providing the above-indicated componentsin the indicated respective range amounts.

In one non-limiting embodiment, a fluid composition is formulatedincluding the above-indicated four components (i.e., alkoxylated amine,dihydrocarbyl phosphite, metallic detergent, and phosphorylatedsuccinimide) such that the fluid composition comprises a viscosity at100° C. of <6 cSt, a viscosity at 40° C. of <30 cSt, and a BrookfieldViscosity at −40° C. of <10,000 cP, wherein the ∂μ/∂T slope value isdetermined from coefficient of friction and temperature measurementstaken on an SAE #2 Machine using a paper friction material lined clutchplate and testing conditions of 0.79 N/mm², >50 rpm, and at 40° C. and120° C.

As can be appreciated from these foregoing descriptions and thedescriptions and experimental studies reported infra, this inventionalso provides a fluid composition for power transmissions employing afriction torque transfer apparatus which can meet requirements for highstatic and quasi-static friction while also minimizing tendency for NVHphenomena which otherwise may arise. The fluid compositions of thepresent invention are advantageously suited for use in friction torquetransfer devices requiring higher quasi-static friction conditions,which have an increased tendency for NVH phenomena.

In another embodiment, a method is provided for reducing NVH in a powertransmission apparatus having a friction torque transfer apparatus, suchas any of the above-indicated clutching mechanisms, comprisingmaintaining a negative ∂μ/∂P slope during engaging, slipping ormodulating thereof, where “P” represents the pressure on the clutchsurfaces

The foregoing general description and the following detailed descriptionare exemplary and explanatory only and are intended to provide furtherexplanation of the present invention, as claimed.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram of a power train model for clutch engagement inaccordance with an embodiment of the invention.

FIG. 2 is a graph of a unit impulse response of a 2^(nd) Order LTIsystem of a power train model according to an embodiment of theinvention.

FIG. 3 is a graph of a unit step response of a 2^(nd) Order LTI systemof a power train model according to an embodiment of the invention.

FIGS. 4-10 are plots of squawk pressure versus ∂μ/∂T as measured atdifferent sliding speeds at a pressure of 0.79 N/mm², respectively. Therespective sliding speeds at which measurements were taken were asfollows: FIG. 4 (5 rpm); FIG. 5 (10 rpm); FIG. 6 (20 rpm); FIG. 7 (50rpm); FIG. 8 (100 rpm); FIG. 9 (200 rpm); and FIG. 10 (250 rpm).

FIG. 11 is plot of R² (for correlation of ∂μ/∂T to squawk pressure)versus sliding speed (v, rpm) for the tests of FIGS. 4-10 conducted atthe test pressure condition of 0.79 N/mm².

FIGS. 12-17 are plots of squawk pressure versus ∂μ/∂T as measured atdifferent sliding speeds at a pressure of 3.40 N/mm², respectively. Therespective sliding speeds at which measurements were taken were asfollows: FIG. 12 (5 rpm); FIG. 13 (10 rpm); FIG. 14 (20 rpm); FIG. 15(50 rpm); FIG. 16 (100 rpm); and FIG. 17 (200 rpm).

FIGS. 18-19 show coefficient of friction μ results observed for theeight test fluids at a pressure of 0.79 N/mm² and at temperatures of 40°C. and 120° C., respectively.

FIG. 20 is a plot of coefficient of ∂μ/∂T (reported as a value that hasbeen multiplied by the number negative one, i.e., “x−1”) versus slidingspeed (v, rpm) at a pressure of 0.79 N/mm².

FIGS. 21-28 are plots of squawk pressure versus ∂μ/∂P as measured atdifferent sliding speeds, temperatures and pressures. For FIGS. 21-24,∂μ/∂P was measured at 40° C. between 3.40 and 0.79 N/mm² at slidingspeeds of 5, 50, 200 and 250 rpm, respectively. For FIGS. 25-28, ∂μ/∂Pwas measured at 120° C. between 3.40 and 0.79 N/mm² at sliding speeds of5, 50, 200 and 250 rpm, respectively.

FIG. 29 shows plots of R² versus sliding speed (v, rpm) for the datareported in FIGS. 21-28, at temperatures of 40° C. and 120° C.,respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Vehicles meeting stringent demands of consumers require durability andperformance in all of the vehicular systems. One of the most importantsystems is the power transmission system (“transmission”) whichtransmits the power generated by the automobile engine to the wheels. Itbeing one of the most complex systems in the vehicle, it is also one ofthe most costly to diagnose, repair, or replace. The transmissionusually includes, inter alia, a clutch with plates, a torque converter,and a plurality of gears to alter the torque and speed relationship ofthe power delivered to the wheels by changing the gear ratio.

Discriminating consumers primarily desire ride comfort, highperformance, low maintenance (high mileage between servicing), andextended life expectancy. However, with the advent of new transmissiontechnologies, old standards of performance which were previously metwith approval are now becoming more challenging and problematic.

For instance, the advent of electronically controlled converter clutch(ECCC) designs, as well as vehicles equipped with a continuouslyvariable transmission (CVT) and advances in aerodynamic body designgenerally result in passenger cars with smaller transmissions which tendto operate with higher energy densities and higher operatingtemperatures. Consumers also are keenly aware of the “feel” of thedriving experience that a vehicle offers. Unusual, abnormal orunexpected vehicular noises, vibrations, and/or ride harshness make thedriving experience less comfortable. Consumers also want serviceintervals for replacing fluids to be extended as much as possiblewithout risking performance or engine equipment integrity. Such changeschallenge lubricant suppliers to formulate automatic transmission fluidswith new and unique performance characteristics. Original equipmentmanufacturers (OEMs) also desire automatic transmission fluids withfrictional characteristics capable of meeting the requirements of ECCC,CVT, and other designs while retaining sufficient performance in regardto anti-NVH, durability, antiwear, etc.

As power transmission fluids are desired which operate underincreasingly severe conditions, the fluids used to lubricate thosetransmissions ideally would be formulated not only to endure highertemperatures and pressures, but also control NVH. To reduce equipmentproblems and increase the interval between transmission fluid changes,the transmission additive packages ideally would be formulated so thatimportant fluid properties change as little as possible during a servicelife in the face of these stresses.

A need exists for an effective way of addressing friction, wear anddurability problems associated with automatic transmissions, such as tomeet the needs of OEM automobile designers and suppliers, for extendedtransmission fluid life and durability while also improving anti-NVH toincrease consumer satisfaction. This invention addresses these and otherneeds.

In one particular non-limiting embodiment, a method is provided forreducing noise-vibration-harshness (“NVH”) in a power transmissionapparatus having a shifting clutch, comprising maintaining a negative∂μ/∂T slope during engagement of the shifting clutch. How this conditionis achieved in the transmission is not particularly limited. It may beachieved via a novel approach in formulating the transmission fluid, asdescribed in more detail elsewhere herein.

The reduction obtained in NVH may be achieved in the form of a reductionof one or more of shift shudder, chatter, squawk, or similar noise,vibration and/or harshness, relative to a reference fluid comprising acommercial ATF product. Under preselected conditions, this negative∂μ/∂T slope has been found to be maintainable without loss of static andquasi-static friction properties at the shifting clutch duringengagement.

For purposes herein, “NVH” collectively refers tonoise-vibration-harshness as those terms are defined herein. “NVHsuppression” refers to a reduction in one or more of noise, vibration,and/or harshness. Chatter, shudder and squawk all originate from avibration(s) within the transmission system and generally are compoundparameters comprised of noise and vibration “Shift chatter”, “chatternoise” or “chatter” for short, refers to a NVH parameter that isgenerally balanced in being observed as both noise and vibration.“Squawk” refers to an NVH parameter predominantly observed as noise andless as vibration. “Squawk pressure” is measured on a ZF GK test rigapparatus, which is commercially available from the ZF Group,Friedrichshafen Germany. The clutch designated by the test rig supplieras the “E-clutch” of a ZF 6HP26 transmission is used in the ZF GK testrig. A test fluid and friction elements are loaded where applicable inthe ZF GK test rig. The test rig includes an on-board computer with aprogrammable, graphical user interface that permits the user to selectand input the desired test conditions under which squawk, staticfriction and quasi-static friction are to be measured, and the testresults are stored by the system in retrievable formats. The ZF-GK Rigtest performed on the apparatus is a test developed by ZF to measureslip controlled clutch opening and closing performance characteristics.An interchangeable intermediate shaft allows the measurement offrictional vibration that is the basis for evaluation of NVHcharacteristics such as squawk of the test fluid. The test uses aprocedure supplied by ZF with the apparatus. For purposes herein, squawkpressure, and is expressed in terms of the threshold pressure beyondwhich squawk phenomena are observed. The higher the value of thisparameter the lower the probability for the noise or vibration phenomenato occur for a given fluid. Illustrations set forth herein may refer tosquawk or “squawk pressure”, although it will be appreciated that theinvention has broader application to noise and vibration (NVH) phenomenain general. Additionally, “Shudder” refers to an NVH parameterpredominantly observed as vibration and less as noise. “Harshness”refers to NVH phenomena that are predominantly sudden (e.g., shock,jerk, clunk, impulse, pop, jolt, bang, etc.) and which may beexperienced by occupants as a sudden, and perhaps brief, noise orvibration or both. “Harshness” is also used by some practitioners torefer to the cumulative effects of noise and vibration on occupantcomfort and fatigue (thus, e.g., a driver is less comfortable and tendsto become fatigued more rapidly in a vehicle with greater harshness).“Static friction” refers to breakaway static coefficient of friction;values thereof described herein are measured on a ZF GK rig.“Quasi-static friction” refers to dynamic end-point coefficient offriction; values thereof described herein are measured on a ZF GK testrig. In general it was found that the noise phenomena decreases withdecreasing quasi-static friction level. Higher quasi-static friction isgenerally desirable for higher torque transmission. “Operating”, as usedherein, includes, but is not limited to, any functional utilization ofthe fluid including transmitting power, lubricating, and wetting.

The discovery that providing and maintaining a negative ∂μ/∂T slopeduring engagement of the shifting clutch can reduce NVH represents asurprising discovery in the power transmission field. The presentinvestigators also have discovered that merely using a transmissionfluid in the operation of a power transmission which yields a positiveslope of coefficient of friction (μ) versus sliding velocity (v) isinadequate to significantly suppress and control NVH. It hassurprisingly been discovered that the transmission fluid used in thetransmission must induce a negative friction dependence on temperaturein the engagement of the clutching mechanism of the power transmissionto suppress NVH in a meaningful manner. This particularly applies, e.g.,to prevention of shift shudder, chatter, or squawk during the engagementof a clutch. It ensures a smooth shift in a clutch when platetemperature at the friction interface is rising during engagement.Provision of negative ∂μ/∂T condition in a transmission makes itpossible to raise the overall value of the coefficient of friction atessentially all or all sliding speeds and at the same time preventsquawk, shudder and chatter from occurring in the clutches. The negative∂μ/∂T condition is important in formulating higher coefficient offriction and higher torque capacity fluids that will still suppress NVH.The significant improvements in torque capacity and NVH suppression mayalso make it possible for transmissions to be smaller and/or operate atlower pressure, all of which improve fuel economy. The discoveredsignificance of the negative ∂μ/∂T condition is not necessarily limitedto any particular modality for providing this prescribed performancecondition.

As another discovery of the present invention, NVH-reduction is obtainedin a power transmission apparatus having a friction torque transferapparatus by maintaining a negative ∂μ/∂P slope during engaging,slipping or modulating thereof.

More detail on the mathematical underpinnings of the above uniqueapproaches to modeling a transmission system is provided below.Mathematical models of friction properties in clutches suggest that thesign (positive or negative) of the slope of the friction coefficient “μ”with respect to temperature “T”, ∂μ/∂T, or pressure, ∂μ/∂P, has oppositeeffects depending on whether the clutch is engaging or disengaging. Forexample, having a positive ∂μ/∂T helps to prevent vibrations when theclutch is releasing, but may promote unstable vibrations when the clutchis engaging. Consequently, the conventional wisdom in the lubricantadditive industry is that the lubricant's friction coefficient should bemade independent of temperature and pressure as much as possible.

I. Noise Phenomena Model

The present invention is based in part on a new and in-depthunderstanding of the specific applications of automatic transmissionfluids to identify which characteristic is more important so that μ-Tand μ-P dependencies can be exploited to improve the automatictransmission fluid's ability to suppress unstable vibrations.

Multiple plate disk clutches are used extensively for shifting gears inautomatic transmissions. During a shift one or more clutches is engagingor disengaging. In these active clutches the automatic transmissionfluid (ATF) and friction material experience large changes in pressure,P, temperature, T, and sliding speed, v. The coefficient of friction, μ,of the ATF and friction material is a function of these variables soμ(v,T,P) also changes during clutch engagement. These changes infriction coefficient can lead to NVH phenomena such as shift shudder,chatter or squawk if the ATF properties and clutch friction material areimproperly selected.

An in-depth theoretical understanding of the cause of NVH in shiftingclutches is crucial in the development of a suitable ATF to work with aparticular friction material. A model has been developed that identifiesthe relationships between ATF friction properties and NVH phenomena suchas squawk. In particular, friction slope with respect to temperature,∂μ/∂T, is identified as a primary factor in squawk. During clutchengagement negative ∂μ/∂T increases the damping and reduces the risk ofself-excited vibration. Experimental data, described below, has beencollected which corroborate this model. The effect of ∂μ/∂T on clutchrelease and the effects of other ATF friction properties are alsodiscussed.

A vehicle power train experiences a combination of torsional and axialvibrations that affect vehicle performance and occupant comfort. Thesevibrations and their effects are major contributors to noise, vibrationand harshness (NVH). Sources of NVH include engine firing pulses, valvemotion, engine vibrations (torsional and axial), and tire-roadinteractions—any of which can excite resonance in the vehicle.Vibrations from these sources are transferred through engine mounts,transmission bearings, drive shaft bearings, tires (via steering) andaxle suspensions to the passenger compartment by way of the vehicleframe, steering wheel or brake pedal. For purposes herein, drivelinevibrations from clutch engagement were analyzed during a gear shift andit was determined how the friction related properties of the ATF andfriction material affect them. The model of temperature in the frictioninterface and the dependence of the coefficient of friction (“μ”) ontemperature (“T”) are major enhancements to the understanding of theeffect of friction properties on the stability (smoothness) of clutchengagement during a gear shift. TABLE A Nomenclature Symbol DescriptionA Total friction surface area = number of friction interfaces inmultiple plate clutch × area of each surface c_(d), c_(t) Intrinsicdamping in driveline, turbine c_(d)* Effective damping in driveline withchanges in μ(v, P, T) c_(ps) Specific heat of steel reaction plate∂μ/∂v, ∂μ/∂P, ∂μ/∂T Partial derivatives of μ(v, P, T) with respect to v,P and T I_(d), I_(t), I_(e) Equivalent inertias of driveline, turbine,engine k_(d) Driveline stiffness L Thickness of steel reaction plate (m)μ(v, P, T) Coefficient of friction of ATF and friction material P(t)Pressure applied (released) to shifting clutch to increase (decrease)torque R Effective radius of friction bands in the clutch (constant) ρDensity (kg/m³) of the steel reaction plate t Time duration of slidingcontact in clutch T_(TC) Total torque transferred by torque converterand torque converter clutch T_(CL) = μARP Torque transferred by shiftingclutch T Temperature of ATF and friction material τ Time constant ofsliding speed response: v(t) = v₀e^(−t/τ) v(t) = R(ω_(t)(t) − ω_(d)(t))Linear sliding speed in the shifting clutch ω_(d)(t), ω_(e)(t), ω_(t)(t)Driveline, engine, and turbine rotational speeds _(ωv) Constantreference speed at opposite end of clutch output shaft

The major components of an automotive power train equipped with anautomatic transmission are shown in FIG. 1. The engine transfers powerto the transmission through the torque converter (TC) and torqueconverter clutch (TCC). The engine has inertia I_(e) and turns at speedω_(e)(t). The turbine includes the components from the torque converter(excluding components tied to the engine) to the clutch pack involved inthe shift. The specific clutch involved in the shift is arbitrary aslong as only one clutch is engaging, as is typical. The specific valuesof the model parameters depend on which gears are involved. Componentspast the clutch are part of the driveline. The turbine components haveinertia I_(t), viscous damping c_(t) and speed ω_(t)(t), and areconsidered rigid (infinitely stiff) relative to the driveline. Thedriveline has inertia I_(d), damping c_(d), stiffness k_(d), and angularvelocity ω_(d)(t). The vehicle is represented as having a constant speedduring the shift. The constant speed ω_(v) may be chosen to representany point of interest, e.g., the gear end of the clutch output shaft.The specific gears involved in the shift and the choice of referencespeed location affect how the inertias of the driveline components aredistributed, some included in I_(d) and some in the vehicle, and thevalues of the damping and stiffness parameters, but they do not affectthe friction characteristics or fundamental dynamics of the system.

Before an up-shift occurs the turbine is connected to the vehicle by theprevious gear with a higher gear ratio, so the turbine initially rotatesat a higher speed than the representative vehicle speed, ω_(t)(0)>ω_(v).When the transmission shifts to a higher gear one clutch pack disengagesand another engages, and the NVH phenomena under consideration arecaused by friction in the engaging clutch plates. The torque transferfrom the engine to the turbine is through the torque converter (T_(TC)),which has two parallel torque paths: 1) the fluid coupling between thepump and turbine impellers; and 2) the friction torque in the torqueconverter clutch (T_(CL)). The clutch torque is controlled by pressureand the ATF friction characteristics. The model represents that thevibrations as predominantly torsional, although axial effects that mightinfluence the motion can be introduced as pressure oscillations thatcause forced torsional vibrations.

For analyzing squawk and shudder vibrations, in this study focus islimited to the driveline. The engine and turbine motions can becomeunstable, but since they are considered rigid (relative to the flexibledriveline) they are not sources of vibration.

From Newton's second law the driveline equation of motion is:$\begin{matrix}{{I_{d}{\overset{.}{\omega}}_{d}} = {T_{CL} - {c_{d}\left( {\omega_{d} - \omega_{v}} \right)} - {k_{d}{\int_{0}^{t}{\left( {{\omega_{d}(\tau)} - \omega_{v}} \right){\mathbb{d}\tau}}}}}} & (1)\end{matrix}$where the instantaneous clutch torque is:T _(CL) =μARP(t).  (2)

The integral of the velocity difference between the two ends of theclutch output shaft gives the total twist in the shaft. The twist in theshaft multiplied by the shaft stiffness equals the reaction torque ofthe shaft on inertia I_(d).

Traditional stability analysis about an equilibrium condition isinappropriate for the unsteady (non-equilibrium) conditions during agear shift. However, if the velocity is sufficiently damped the shiftwill not experience vibrations due to step or ramp changes in pressure.(There can be forced vibrations if there are pressure oscillations.)Consequently, an additional time derivative of equation (1) is taken totransform it into a second order differential equation in the variableω_(d), which represents the output angular velocity of the clutch, andto consider the effective damping of the equation.

The time derivative of ω_(v) is zero since it is constant, and thederivative is the inverse of the integration, so taking the derivativeof equation (1), applying the chain rule to T_(CL) (=μARP) andrearranging terms yields:I _(d){umlaut over (Ω)}_(t) +c _(d){dot over (ω)}_(d) +k _(d)ω_(d) =k_(d)ω_(v) +{dot over (μ)}ARP+μAR{dot over (P)}  (3)

The coefficient of friction, μ(v,T(v),P), is a function of slidingspeed, v, pressure, P, and temperature, which also depends on slidingspeed, T=T(v). Consequently, the time derivative of μ is:$\begin{matrix}{\overset{.}{\mu} = {{\frac{\partial\mu}{\partial v}\overset{.}{v}} + {\frac{\partial\mu}{\partial T}\frac{\mathbb{d}T}{\mathbb{d}v}\overset{.}{v}} + {\frac{\partial\mu}{\partial P}\overset{.}{P}}}} & (4)\end{matrix}$Sliding speed: v=R(ω_(t)−ω_(d)) so:{dot over (v)}=R({dot over (ω)}_(t)−{dot over (ω)}_(d))  (5)Using equations (4) and (5), equation (3) becomes: $\begin{matrix}{{{I_{d}{\overset{¨}{\omega}}_{d}} + {c_{d}^{*}{\overset{.}{\omega}}_{d}} + {k_{d}\omega_{d}}} = {{k_{d}\omega_{v}} + {{{AR}\left( {\mu + {P\frac{\partial\mu}{\partial P}}} \right)}\overset{.}{P}} + {{AR}^{2}{P\left( {\frac{\partial\mu}{\partial v} + {\frac{\partial\mu}{\partial T}\frac{\mathbb{d}T}{\mathbb{d}v}}} \right)}{\overset{.}{\omega}}_{t}}}} & (6)\end{matrix}$where the effective damping is given by $\begin{matrix}{c_{d}^{*} = {c_{d} + {{AR}^{2}{P\left( {\frac{\partial\mu}{\partial v} + {\frac{\partial\mu}{\partial T}\frac{\mathbb{d}T}{\mathbb{d}v}}} \right)}}}} & (7)\end{matrix}$Instantaneous temperature variations at the friction interface aredefined approximately as: $\begin{matrix}{{dT} = {\frac{2\quad\mu\quad{vP}}{\rho\quad c_{ps}L} \cdot {dt}}} & (8)\end{matrix}$and instantaneous variations in sliding speed are:dv={dot over (v)}·dt  (9)so $\begin{matrix}{\frac{\mathbb{d}T}{\mathbb{d}v} = {\frac{2\quad\mu\quad P}{\rho\quad c_{ps}L}\frac{v}{\overset{.}{v}}}} & (10)\end{matrix}$Substituting equation (10) into (6) and (7), the equation of motionbecomes: $\begin{matrix}{{{I_{d}{\overset{¨}{\omega}}_{d}} + {c_{d}^{*}{\overset{.}{\omega}}_{d}} + {k_{d}\omega_{d}}} = {{k_{d}\omega_{v}} + {{{AR}\left( {\mu + {P\frac{\partial\mu}{\partial P}}} \right)}\overset{.}{P}} + {{AR}^{2}{P\left( {\frac{\partial\mu}{\partial v} + {\frac{\partial\mu}{\partial T}\frac{2\mu\quad P}{\rho\quad c_{ps}L}\frac{v}{\overset{.}{v}}}} \right)}{\overset{.}{\omega}}_{t}}}} & (11)\end{matrix}$and the effective damping is: $\begin{matrix}{c_{d}^{*} = {c_{d} + {{AR}^{2}{P\left( {\frac{\partial\mu}{\partial v} + {\frac{\partial\mu}{\partial T}{\frac{2\quad\mu\quad P}{\rho\quad c_{ps}L} \cdot \frac{v}{\overset{.}{v}}}}} \right)}}}} & (12)\end{matrix}$

Equations (11) and (12) describe the relationship between ATF frictionproperties, ∂μ/∂v and ∂μ/∂T, and shift quality as measured by the outputspeed of the clutch.

The clutch output speed is determined by the forcing terms on the righthand side of equation (11), by the damping coefficient equation (12),and by the inertia (I_(d)) and stiffness (k_(d)) coefficients. Equation(11) is a 2^(nd) order differential equation in the unknown motionvariable ω_(d). When the coefficients (I_(d), c_(d)*, k_(d)) of theunknown motion variable are all constant, the equation is referred to as“linear” and “time-invariant” (LTI). The time-invariance refers to thecoefficients. The motion variable does vary with time. If thecoefficients are time-dependent, but do not depend on the motionvariable, the equation is still linear, but not time-invariant. Equation(11) is both nonlinear (the damping coefficient, c_(d)*, depends on theunknown motion variable) and time-variant (the damping coefficientchanges with time). It is not typically possible to find analyticalsolutions to nonlinear time-varying equations; computer solutions aregenerally required. Nevertheless, if the nonlinearity or time-varianceis not strong, it is often possible to approximate the solution of anonlinear time-varying equation with the solution of an LTI equation.Here the behavior of 2^(nd) order LTI systems to impulse and step inputsis first considered, then the implications of the nonlinear dampingcoefficient are considered.

The “inputs” to an equation are the terms on the right-hand-side thatforce the system to deviate from some equilibrium condition. In equation(11) the final equilibrium condition is reached when all terms with timederivatives are zero (none of the variables are changing with time), andthe clutch output speed, ω_(d), is equal to the constant referencespeed, ω_(v), due to the first input k_(d)ω_(v), which is constant. Thesecond or middle input on the right-hand-side of (11) is referred tohere as the {dot over (P)} input, and the right-most input is referredto as the {dot over (ω)}_(t) input.

The engagement of the clutch is controlled through the pressure, P. If Pis zero the clutch output shaft is not connected to the turbine, and the{dot over (P)} and {dot over (ω)}_(t) inputs are zero. In a typicalengagement, the pressure is “stepped up” quickly to connect the turbineto the clutch output shaft. This has the effect of switching the {dotover (ω)}_(t) input from zero to nonzero. If this nonzero value remainedconstant it would look like a stair step and be called a “step input.”The sudden jump in P makes the {dot over (P)} input very large for avery brief period of time, and then it returns to zero when P reachesits constant target value. This is an “impulse input;” a sudden hit withhigh amplitude but short duration.

The solution of 2^(nd) order LTI systems (the “response” of the system)to impulse and step inputs depends primarily on the damping ratio, ζ,which for equation (11) is: $\begin{matrix}{\zeta = \frac{c_{d}^{*}}{2\sqrt{k_{d}I_{d}}}} & (13)\end{matrix}$treating the damping coefficient c_(d)* as constant. A 2^(nd) ordersystem is typically classified according to its damping ratio and thecorresponding free response to an initial displacement with no forceinputs on the right-hand-side:

ζ<0 Negative damping, unstable (response amplitude increases with time)

ζ=0 Undamped, non-decaying vibrations at the natural frequency

0<ζ<1 Underdamped, decaying vibrations at the damped natural frequency

ζ=1 Critically damped, minimum damping level to suppresses vibration.With critically damped and overdamped systems it is still possible tohave vibration if the inputs create “forced” vibration. It is alsopossible to get one oscillation in the free response if the initialvelocity is in the opposite direction of the initial displacement.

ζ>1 Overdamped, no vibration, but slower convergence to steady statethan in the critically damped case (ζ=1).

If the system starts from equilibrium (a constant or steady speed inthis case), the vibration characteristic of the free response alsoapplies to the impulse and step responses. To completely suppresstransient vibration it is necessary for the system to be criticallydamped or overdamped.

FIGS. 2 and 3 show the predicted response of a LTI 2^(nd) order system(clutch output speed in rad/s) to unit impulse and unit step inputs(“unit” inputs have an amplitude of ‘1’) for three different dampingratios. The parameter values used for the simulations are:I _(d)=2 kg·m²

k_(d)=12,700,000 N·m/rad (natural frequency=401 Hz)

c_(d)*=1,008 N·m·s/rad (ζ=0.1, underdamped)

-   -   10,080 N·m·s/rad (ζ=1.0, critically damped)    -   15,120 N·m·s/rad (ζ=1.5, overdamped).

All of these are stable responses. The clutch output speed converges tothe desired value. Stability, however, is insufficient to ensure asmooth shift without vibrations. To suppress vibration for impulse andstep inputs it is necessary to have a damping coefficient that providescritical or overdamping (ζ≧1):c _(d)*≧2√{square root over (k _(d) I _(d))}

Equation (14) shows that to suppress NVH c_(d)* in equation (12) shouldbe as positive as possible. NVH during a shift is evidence that equation(14) is not satisfied, not necessarily that the system is unstable,although it may be.

The nonlinearity and time-variation in c_(d)* is driven largely by v and{dot over (v)}. Once P is applied it is held relatively constant, andthe variation in μ is much smaller than the variation in v and {dot over(v)}. It also is assumed that ∂μ/∂T is relatively constant. The slidingspeed during shift follows an approximately exponential decay:v(t)=v ₀ e ^(−t/τ)  (15)where τ is the “time constant,” a measure of how quickly the slidingspeed converges from initial speed, v₀, to zero.

If the sliding speed has the form given in equation (15), then the rateof change of sliding speed is: $\begin{matrix}{{\overset{.}{v}(t)} = {\frac{- v_{0}}{\tau}{\mathbb{e}}^{{- t}/\tau}}} & (16)\end{matrix}$and the v/{dot over (v)} ratio in equations (11) and (12) ratio is:$\begin{matrix}{\frac{v(t)}{\overset{.}{v}(t)} = {- \tau}} & (17)\end{matrix}$where τ is a positive constant. Equation (17) suggests that even thoughv and {dot over (v)} depend on the unknown speeds ω_(d) and ω_(t) (andtheir derivatives), the ratio v/{dot over (v)} does not. In this casec_(d)* no longer depends on the unknown variable of motion and theequation is linear, although it may still vary with time.

In this case equations (11) and (12) may be simplified further to:$\begin{matrix}{{{I_{d}{\overset{¨}{\omega}}_{d}} + {c_{d}^{*}{\overset{.}{\omega}}_{d}} + {k_{d}\omega_{d}}} = \begin{matrix}{\quad{{k_{\quad d}\quad\omega_{\quad v}}\quad + \quad{{AR}\quad\left( {\mu\quad + \quad{P\quad\frac{\partial\mu}{\partial P}}} \right)\quad\overset{.}{P}}\quad +}\quad} \\{\quad{{AR}^{\quad 2}\quad{P\left( \quad{\frac{\partial\mu}{\partial v}\quad - \quad{\frac{\partial\mu}{\partial T}\quad\frac{2\quad\mu\quad P\quad\tau}{\quad{\rho\quad c_{ps}\quad L}}}} \right)}\quad{\overset{.}{\omega}}_{t}}}\end{matrix}} & (18) \\{c_{d}^{*} = {c_{d} + {{AR}^{2}{P\left( {\frac{\partial\mu}{\partial v} - {\frac{\partial\mu}{\partial T}\frac{2\mu\quad P\quad\tau}{\rho\quad c_{ps}L}}} \right)}}}} & (19)\end{matrix}$

Equation (19) demonstrates that ∂μ/∂T must be negative to increase thedamping. All the parameters in the expression multiplying ∂μ/∂T arepositive, so ∂μ/∂T is the only parameter that can be made negative toensure that c_(d)* is as positive as possible. If the magnitude of thenegative ∂μ/∂T becomes too large (in absolute value), torque capacitymay become reduced. Thus, small negative values of ∂μ/∂T areparticularly desirable.

The ∂μ/∂v term in equation (19) is the μ-v gradient at constanttemperature, which should also be as positive as possible. The ∂μ/∂Tterm is the contribution of the ATF temperature dependence to the totalμ-v gradient, dμ/dv. The contribution of ∂μ/∂T to the overall dampingdepends on the temperature rise in the fluid, which is controlled by theheat generation (μvP), the thermal capacity of the steel reaction plate(ρc_(ps)L), and the duration of the shift (larger τ means a longer shifttime). In general, the more negative ∂μ/∂T the greater the damping atall sliding speeds and pressures, and consequently, the greater NVHsuppression, e.g., greater squawk resistance, that is predicted andexpected from the model.

Experimental data, described in the Examples below, confirm thispredictive model insofar as the provision of negative ∂μ/∂T conditionimproves squawk performance in a transmission.

The coefficients of ∂μ/∂T in the exponential curve fits shown FIGS.4-10, which are discussed in more detail in the Examples section,provide an additional validation of the temperature model in equation(8), and the resulting damping equation (12). This coefficientrepresents the degree to which the ∂μ/∂T term controls stability, andshould have the same dependencies as the parameters multiplying ∂μ/∂T inequation (12). One of those parameters is the sliding speed, v, whichwas also one of the experimental parameters. Equation (12) predicts thatthe damping should be approximately proportional to v. The coefficientsof ∂μ/∂T from the curve fits in the FIGS. 4-10 are plotted versussliding speed in FIG. 20, which shows good linear correlation aspredicted. The model also predicts that the factor multiplying ∂μ/∂Twill increase with pressure. FIG. 20 gives one data point at a higherpressure (3.4 MPa), which shows the expected increase.

From equation (12) it is indicated that positive ∂μ/∂T is desired forsmooth disengagement since {dot over (v)} is positive when the clutchreleases. However, when the clutch releases the pressure drops and thereis no input energy (turbine torque) to cause self-excitation. The shaftwill unwind when it is no longer carrying torque, so there is a risk ofvibration due to this unwinding. There is also a risk that for acontrolled release—an effort to carefully exchange the load between thereleasing and engaging clutches—negative ∂μ/∂T may cause a faster thanexpected drop in torque in the releasing clutch.

These risks will generally be much less than the risk of engagementvibrations since energy absorbed by the clutch and the heat generatedare much greater during engagement. On disengagement, the damping shouldnot become negative because there is no source of energy to create thatunstable condition.

The squawk engagements are performed at constant pressure, so it isdifficult to discern how important ∂μ/∂P might be from squawk test data.The importance of ∂μ/∂P on shift quality depends on how the transmissioncontrol unit applies the pressure. If the pressure is stepped upsuddenly then held constant, as in the squawk test, ∂μ/∂P will not beparticularly important. If the pressure is ramped up, linearly orexponentially, then ∂μ/∂P may also be important. If pressure and slidingspeed change together in a predictable way, then, following the sameanalysis as for temperature, the damping term will include(∂μ/∂P)(dP/dv) so that equation (19) becomes: $\begin{matrix}{c_{d}^{*} = {c_{d} + {{AR}^{2}{P\left( \quad{\frac{\partial\mu}{\partial v}\quad - \quad{\frac{\partial\mu}{\partial T}\quad\frac{2\quad\mu\quad P\quad\tau}{\quad{\rho\quad c_{ps}\quad L}}} + {\frac{\partial\mu}{\partial P}\frac{\mathbb{d}P}{\mathbb{d}v}}} \right)}}}} & (20)\end{matrix}$

Typically an increase in pressure (positive dP) causes a decrease insliding speed (dv negative) so that (dP/dv) is negative. Consequently,if ∂μ/∂P has any effect, it is beneficial for it to be negative. Squawkpressure versus ∂μ/∂P was plotted and a very slight correlation wasfound between increased squawk pressure (better performance) andnegative ∂μ/∂P. FIG. 20 includes a plot of some of those coefficients.It shows that ∂μ/∂P is much less important for squawk performance than∂μ/∂T, but that is expected since the pressure is approximatelyconstant.

Plots of squawk pressure versus ∂μ/∂T in FIGS. 4-10 show that there is ageneral trend for ∂μ/∂T to decrease in magnitude (converge toward zero)at increasing sliding speeds. In test fluids with negative ∂μ/∂T thevalue of ∂μ/∂T was more negative a lower sliding speeds and lessnegative at higher sliding speeds. Consequently, ∂μ/∂T is dependent onsliding speed. This may also be interpreted as temperature dependencesince sliding speed and temperature are linearly related (for constant Pas in the squawk tests).

Although not desiring to be bound to theory, it is more likely that thereduction in ∂μ/∂T (FIGS. 4-10) is temperature dependence for at leasttwo reasons. First, the sliding speeds referred to in the plots aresliding speeds from the SAE#2 test, not clutch engagement sliding speedsfrom the squawk test. Consequently, the sliding speeds are reallyindicating the amount of friction work and heating in the SAE #2 test.Second, the values of ∂μ/∂T at higher pressure are also reduced inmagnitude. Equation (8) says that higher pressure also creates moreheat, so the pressure dependence in ∂μ/∂T from the SAE #2 data may alsobe temperature dependence. All the data are consistent with theinterpretation that ∂μ/∂T decreases in magnitude (becomes less negative)as temperature increases.

The effect of ∂μ/∂T decreasing (in magnitude) with increasingtemperature is that the contribution of the ∂μ/∂T term to the damping inequation (12) decreases during engagement. However, as long as ∂μ/∂Tremains negative it still contributes to positive damping and improvesthe smoothness and stability of the shift. Furthermore, since thevariation in ∂μ/∂T with temperature is linear and predictable, it iseasily handled by the transmission control module.

Accordingly, physical and mathematical models are presented herein ofthe mechanical components in a transmission involved in the shifting ofa clutch. The clutch torque is modeled with a coefficient of frictionthat depends on sliding speed, temperature and pressure: μ=μ(v, T, P). Amajor advance in this model is that the temperature rise in the clutchinterface is modeled, which is shown to be proportional to the productμvP (heat generation per unit area) and inversely proportional to V (therate of change of sliding speed) and ρc_(ps)L (the thermal mass or heatcapacity of the steel reaction plate).

The most significant conclusion of the analysis is that it is importantfor ∂μ/∂T, a property of the ATF and friction material, to be negativeto ensure a smooth, stable shift. It is shown that negative ∂μ/∂Tincreases the damping in the system during engagement and that increaseddamping reduces the risk of vibration. The equations of motion aresolved using several sample sets of data (for illustrative purposes; notbased on actual data) and plots show the reduction in vibration withincreased damping.

Experimental data, summarized in FIGS. 4-10 also validate several keyelements of the model. In particular, with respect to the fluid tested,the data show a strong correlation between improved squawk performanceand more negative ∂μ/∂T. Furthermore, the curve fits of squawkperformance to ∂μ/∂T show that the contribution of ∂μ/∂T to squawkperformance (increased damping) is linearly proportional to slidingspeed, which is predicted by the model. Sliding speed is the dominantparameter controlling the heat generation and temperature (in μvP) sinceP is constant and the changes in μ are small compared to the changes inv. The data suggest that ∂μ/∂T becomes less negative as the temperatureincreases (higher P, sliding at constant higher v), so that thecontribution of ∂μ/∂T to the damping diminishes during the shift. Thistrend can be tolerated as long as ∂μ/∂T does not become positive duringengagement.

The model indicates that negative ∂μ/∂T has the reverse effect when theclutch releases. It reduces the damping and increases the risk ofnegative damping. When the clutch releases there is also the likelihoodof vibration arising due to unwinding of the shaft as the torque on itis released. Both of these effects can be reduced by allowing thepressure to drop quickly. In that case the ∂μ/∂T term in the dampingexpression goes to zero, so ∂μ/∂T does not contribute to negativedamping. Also, dropping the pressure takes the shaft out of thedriveline so that any transient “unwinding” vibrations are not in thetorque path of the power train. This solution is less attractive whenthere is a control strategy to gradually shift the torque transfer fromthe releasing to the engaging clutch. In this case the calibrationengineer needs to determine the rate of pressure drop in the releasingclutch based on how long the releasing clutch can remain stable.

The present invention recognizes that for shifting clutches theengagement is the critical process, not the release or disengagement. Inthe case of shifting clutch, the primary heat and pressure increasesoccur when the clutch is engaging. During disengagement the pressure and“apply” force are dropping so there is much less heat generation.Consequently, lubricants can be specifically formulated with negativevalues of and ∂μ/∂T (and ∂μ/∂P) in order to suppress noise and vibrationduring engagement. This runs counter to the conventional wisdom in thelubricant additive industry that seeks to make the lubricant'scoefficient of friction, μ, as independent of P and T as possible, whichis based on a failure to recognize which process (engagement or releaseof the clutch) is more critical.

Furthermore, since negative ∂μ/∂T make it possible to suppress noise andvibration during clutch engagement, this technology will also allow theformulation of lubricants with higher overall levels of friction (μ), sothat the torque capacity of the clutches (and the whole transmission) inincreased. Alternatively, higher levels of friction permit transmissioncalibration engineers to reduce the operating pressure in thetransmission without sacrificing the torque capacity, which improvesfuel economy and prolongs the life of lubricant and the mechanicalcomponents. Also, higher levels of friction permit smaller transmissionsto be used without compromising torque capacity, which also improvesfuel economy, weight, and material cost.

Although illustrated herein by way of a shifting clutch, it will beappreciated that the above-indicated inventive methodology of providingnegative ∂μ/∂T, or negative ∂μ/∂P, condition in a power transmission isapplicable to friction torque transfer apparatus in general, including,for example, a shifting clutch, a starting clutch, a torque converterclutch, a band clutch, disk or plate clutch, a limited slip differentialclutch, and so forth. The types of power transmission in which theinventive methodology may be applied are not particularly limited, andinclude, e.g., automatic transmissions, manual transmissions,continuously variable transmissions, and manual automatic transmissions,and so forth. A friction torque apparatus may also operate in differentmodes, such as continuously slipping, modulating on-off, and engagingfrom slipping to lock-up, These transmissions may be used in a varietyof applications such as automotive, marine, aerospace, industrial, andso forth. In a particular embodiment, the inventive method is applied toa multi-speed automatic transmission, such as a 4-speed or moretransmission. In one embodiment, it may be selected from the groupconsisting of a 5-speed automatic transmission, a 6-speed automatictransmission, and a 7-speed automatic transmission, and particularly6-speed automatic transmissions. The transmission apparatus also maycomprise a dual-clutch transmission or a heavy duty automatictransmission.

In the instance of a shifting clutch as the friction torque transferapparatus, the clutch may comprise a lining material comprising anysuitable wet friction material such as paper, steel, carbon, orelastomeric, etc. Paper friction materials for clutch liners arecommercially available. They generally are produced by the steps ofmaking wet paper from a fiber base material of natural pulp fiber,organic synthetic fiber, inorganic fiber, etc. and a filler and frictionadjustor such as diatomaceous earth, gum, etc.; impregnating the wetpaper with a resin binder of a heat-curable resin; and thermallyhardening the wet paper. One observation of the invention is that paperfriction materials tend to be harder than carbon fiber frictionmaterials, and that variation in pressure does not influence squawk assignificantly as variation in temperature with respect to clutches linedwith paper friction materials.

II. ATF Compositions

In one embodiment, appropriate selection of a transmission fluidformulation for lubricating a shifting clutch or other friction torquetransfer apparatus during operation of the transmission apparatus isresponsible for providing the condition of a negative ∂μ/∂T (or negative∂μ/∂P) during engagement of the shifting clutch. That is, additive andfluid compositions have been developed for transmissions to provide highstatic and quasi-static friction properties while minimizing NVHcharacteristics such as shift noise, shudder, chatter and squawk. Thesecompositions are also effective at providing the same degree of NVHsuppression performance after aging of the fluid. Although the additivecomposition components described below are described occasionally withreference to a function, that function may be one of other functionsserved by the same component and should not be construed as a mandatorylimiting function.

A. Additive Package I for Enhanced Anti-NVH Performance:

In one embodiment, an anti-NVH performance-improving additive packagecomprises four critical components: alkoxylated amine friction modifier,dihydrocarbylphosphite friction modifier, metallic detergent, andphosphorylated succinimide ashless dispersant.

Experimental studies were conducted, which are summarized in more detailin the Examples section herein, which revealed that these fourcomponents of an automatic transmission fluid are primarily responsiblefor influencing the ∂μ/∂T (and ∂μ/∂P) values observed. In particular,properly balanced combinations of these four particular components havebeen discovered to have the unexpected combined effect of bringing aboutthe negative ∂μ/∂T slope condition during engaging, slipping ormodulating of a friction torque transfer apparatus of the transmissionapparatus, which condition surprisingly has been found to provide NVHsuppression without quasi-static or static friction losses ofsignificance. Indeed, it has been observed that providing evenrelatively small negative ∂μ/∂T values yield very significantimprovements in anti-NVH. Although higher magnitude negative ∂μ/∂Tvalues also may provide some additional incremental improvements inanti-NVH, the most significant gains in NVH suppression generally can beattained at relatively small negative ∂μ/∂T conditions. The respectiveamounts of these four components needed to attain the negative ∂μ/∂Tslope condition generally are governed by the experimental discovery andobservation that the presence of alkoxylated amine, dihydrocarbylphosphite, and metallic detergent independently increase the negativevalue of ∂μ/∂T, i.e., make it more negative, while a decreasing levelthereof has the opposite effect on ∂μ/∂T, i.e., makes it less negative(i.e., a negative value of smaller absolute magnitude or apositive-value). On the other hand, increasing amounts of thephosphorylated succinimide component make ∂μ/∂T less negative, whiledecreasing amounts have the opposite effect. Levels of these fourcomponents must be balanced with above criteria in mind to introduce anegative ∂μ/∂T condition, preferably a small negative ∂μ/∂T conditionfor improving anti-NVH performance, among other things. Lesser includedcombinations of these four components will not behave reliably in theabove indicated manner.

Component (A): Friction Modifier (1)

Component (A) comprises an alkoxylated amine friction modifier which isused in the additive package and transmission fluids of the presentinvention. Increasing the level of this component in the transmissionfluid has been found to make ∂μ/∂T more negative, and decreasing itslevel has the opposite effect.

The alkoxylated amines which may be utilized in the practice of thisinvention are preferably primary aliphatic amines that have beenethoxylated or propoxylated. The resultant product is thus anN,N-bis(hydroxyalkyl)-N-aliphatic amine in which the aliphatic group ispreferably an alkyl or alkenyl group containing from 10 to 22 carbonatoms, most preferably an alkyl or alkenyl group containing from 16 to18 carbon atoms. N,N-bis(hydroxyethyl)-N-tallow amine is especiallypreferred. Examples of suitable alkoxylated amine friction modifiers aredescribed, for example, in U.S. Pat. No. 4,855,074, which descriptionsare incorporated herein by reference.

The alkoxylated amine compounds of the invention should be used at aconcentration of about 0.002 wt % to about 0.5 wt %, particularly about0.01 wt % to about 0.25 wt %, to insure that the finished blend containsan adequate quantity of the foregoing ingredient although smalleramounts may be successfully employed, depending on the relative amountsof components (B), (C) and (D).

Component (B): Friction Modifier (2)

Dihydrocarbylphosphites are used as an additional friction modifier inthe additive package and transmission fluids of the present invention.Increasing the level of this component in the transmission fluid hasbeen found to make ∂μ/∂T more negative, and decreasing its level has theopposite effect.

As used herein “hydrocarbyl” is an alkyl, alkaryl, aralkyl, alkenyl,cycloalkyl or cycloalkenyl group. Dihydrocarbylphosphites usable in thisinvention include phosphite derivatives such as dialkylphosphites,dicycloalkylphosphites, diallyl phosphites, diarylphosphites,diaralkylphosphites, monoalkylmonoarylphosphites, and the like.Illustrative compounds of this type include dimethylphosphite,diethylphosphite, dipropyl phosphite, dibutylphosphite,dioctylphosphite, dicyclohexylphosphite, diphenylphosphite, dioleylphosphite, methyl oleyl phosphate, butyl lauryl phosphate, ethyl hexylphosphate, napthyl oleyl phosphite, dibenzylphosphite,phenylneopentylphosphite, diamyl phosphate, dihexyl phosphate, diheptylphosphate, di-2-ethylhexyl phosphate, diisoctyl phosphate, didecylphosphate, dilauryl phosphate, didecenyl phosphate, didodecenylphosphate, distearyl phosphate, dieicosyl phosphate, dicresyl phosphate,dicyclohexenyl phosphate, and dinonylphenyl phosphite and anycombinations of the above. Examples of suitable dihydrocarbyl phosphitefriction modifiers are described, for example, in U.S. Pat. Nos.4,855,074, and 4,588,415, which descriptions are incorporated herein byreference.

The dihydrocarbyl phosphite compounds of the invention should be used ata concentration of about 0.001 wt % to about 0.5 wt %, particularlyabout 0.01 wt % to about 0.2 wt %, to insure that the finished blendcontains an adequate quantity of the foregoing ingredient althoughsmaller amounts may be successfully employed, depending on the relativeamounts of components (A), (C) and (D).

Component (C): Metallic Detergent

A metallic detergent is included in the additive package andtransmission fluids of the present invention. Increasing the level ofthis detergent component in the transmission fluid has been found tomake ∂μ/∂T more negative, and decreasing its level has the oppositeeffect.

A suitable metallic detergent may include an oil-soluble neutral oroverbased salt of alkali or alkaline earth metal with one or more of thefollowing acidic substances (or mixtures thereof): (1) a sulfonic acid,(2) a carboxylic acid, (3) a salicylic acid, (4) an alkyl phenol, (5) asulfurized alkyl phenol, and (6) an organic phosphorus acidcharacterized by at least one direct carbon-to-phosphorus linkage. Suchan organic phosphorus acid may include those prepared by the treatmentof an olefin polymer (e.g., polyisobutylene having a molecular weight ofabout 1,000) with a phosphorizing agent such as phosphorus trichloride,phosphorus heptasulfide, phosphorus pentasulfide, phosphorus trichlorideand sulfur, white phosphorus and a sulfur halide, or phosphorothioicchloride.

Suitable salts may include neutral or overbased salts of magnesium,calcium, or zinc. As a further example, suitable salts may includemagnesium sulfonate, calcium sulfonate, zinc sulfonate, magnesiumphenate, calcium phenate, and/or zinc phenate. See, e.g., U.S. Pat. Nos.6,482,778 and 5,578,235, which descriptions are incorporated herein byreference.

Oil-soluble neutral metal-containing detergents are those detergentsthat contain stoichiometrically equivalent amounts of metal in relationto the amount of cidic moieties present in the detergent. Thus, ingeneral the neutral detergents will have a low basicity when compared totheir overbased counterparts. The acidic materials utilized in formingsuch detergents include carboxylic acids, salicylic acids, alkylphenols,sulfonic acids, sulfurized alkylphenols and the like.

The term “overbased” in connection with metallic detergents is used todesignate metal salts wherein the metal is present in stoichiometricallylarger amounts than the organic radical. The commonly employed methodsfor preparing the overbased salts involve heating a mineral oil solutionof an acid with a stoichiometric excess of a metal neutralizing agentsuch as the metal oxide, hydroxide, carbonate, bicarbonate, or sulfideat a temperature of about 50° C., and filtering the resultant product.The use of a “promoter” in the neutralization step to aid theincorporation of a large excess of metal likewise is known. Examples ofcompounds useful as the promoter include phenolic substances such asphenol, naphthol, alkyl phenol, thiophenol, sulfurized alkylphenol, andcondensation products of formaldehyde with a phenolic substance;alcohols such as methanol, 2-propanol, octanol, ethylene glycol, stearylalcohol, and cyclohexyl alcohol; and amines such as aniline, phenylenediamine, phenothiazine, phenyl-beta-naphthylamine, and dodecylamine. Aparticularly effective method for preparing the basic salts comprisesmixing an acid with an excess of a basic alkaline earth metalneutralizing agent and at least one alcohol promoter, and carbonatingthe mixture at an elevated temperature such as 60° C. to 200° C.

Examples of suitable metal-containing detergents include, but are notlimited to, neutral and overbased salts such as a sodium sulfonate, asodium carboxylate, a sodium salicylate, a sodium phenate, a sulfurizedsodium phenate, a lithium sulfonate, a lithium carboxylate, a lithiumsalicylate, a lithium phenate, a sulfurized lithium phenate, a magnesiumsulfonate, a magnesium carboxylate, a magnesium salicylate, a magnesiumphenate, a sulfurized magnesium phenate, a calcium sulfonate, a calciumcarboxylate, a calcium salicylate, a calcium phenate, a sulfurizedcalcium phenate, a potassium sulfonate, a potassium carboxylate, apotassium salicylate, a potassium phenate, a sulfurized potassiumphenate, a zinc sulfonate, a zinc carboxylate, a zinc salicylate, a zincphenate, and a sulfurized zinc phenate. Further examples include alithium, sodium, potassium, calcium, and magnesium salt of a hydrolyzedphosphosulfurized olefin having about 10 to about 2,000 carbon atoms orof a hydrolyzed phosphosulfurized alcohol and/or analiphatic-substituted phenolic compound having about 10 to about 2,000carbon atoms. Even further examples include a lithium, sodium,potassium, calcium, and magnesium salt of an aliphatic carboxylic acidand an aliphatic substituted cycloaliphatic carboxylic acid and manyother similar alkali and alkaline earth metal salts of oil-solubleorganic acids. A mixture of a neutral or an overbased salt of two ormore different alkali and/or alkaline earth metals can be used.Likewise, a neutral and/or an overbased salt of mixtures of two or moredifferent acids can also be used.

As is well known, overbased metal detergents are generally regarded ascontaining overbasing quantities of inorganic bases, generally in theform of micro dispersions or colloidal suspensions. Thus the term“oil-soluble” as applied to metallic detergents is intended to includemetal detergents wherein inorganic bases are present that are notnecessarily completely or truly oil-soluble in the strict sense of theterm, inasmuch as such detergents when mixed into base oils behave muchthe same way as if they were fully and totally dissolved in the oil.Collectively, the various metallic detergents referred to herein above,are sometimes called neutral, basic, or overbased alkali metal oralkaline earth metal-containing organic acid salts.

Methods for the production of oil-soluble neutral and overbased metallicdetergents and alkaline earth metal-containing detergents are well knownto those skilled in the art, and extensively reported in the patentliterature. See, for example, U.S. Pat. Nos. 4,647,387 and 4,880,550,which descriptions are incorporated herein by reference.

The metallic detergents utilized in this invention can, if desired, beoil-soluble boronated neutral and/or overbased alkali of alkaline earthmetal-containing detergents. Methods for preparing boronated metallicdetergents are described in, for example, U.S. Pat. Nos. 4,965,003 and4,965,004, which descriptions are incorporated herein by reference.

The metallic detergent compounds of the invention should be used at aconcentration of about 0.01 wt % to about 1.0 wt %, particularly about0.01 wt % to about 0.7 wt %, to insure that the finished blend containsan adequate quantity of the foregoing ingredient although smalleramounts may be successfully employed, depending on the relative amountsof components (A), (B) and (D).

Component (D): Dispersant

Component (D) comprises phosphorylated succinimide ashless dispersantwhich is included in the additive package and transmission fluids of thepresent invention. Increasing the level of this component in thetransmission fluid makes ∂μ/∂T less negative, and decreasing its levelhas the opposite effect.

Examples of suitable dispersants are described, for example, in U.S.Pat. Nos. 6,627,584 and 4,857,214, which descriptions are incorporatedherein by reference. These dispersants are formed by phosphorylating anashless dispersant having basic nitrogen and/or at least one hydroxylgroup in the molecule, and preferably a succinimide dispersant. As usedherein the term “succinimide” is meant to encompass the completedreaction product from reaction between one or more polyamine reactantsand a hydrocarbon-substituted succinic acid or anhydride (or likesuccinic acylating agent), and is intended to encompass compoundswherein the product may have amide, amidine, and/or salt linkages inaddition to the imide linkage of the type that results from the reactionof a primary amino group and an anhydride moiety.

The succinimide includes, for example, polyamine succinimides in whichthe succinic group contains a hydrocarbyl substituent containing atleast 30 carbon atoms are described for example in U.S. Pat. Nos.3,172,892; 3,202,678; 3,216,936; 3,219,666; 3,254,025; 3,272,746; and4,234,435, which descriptions are incorporated herein by reference. Alsoincluded are alkenyl succinimides, which may be formed by conventionalmethods such as by heating an alkenyl succinic anhydride, acid,acid-ester, acid halide, or lower alkyl ester with a polyaminecontaining at least one primary amino group. The alkenyl succinicanhydride may be made readily by heating a mixture of olefin and maleicanhydride to, for example, about 180-220° C. The olefin is preferably apolymer or copolymer of a lower monoolefin such as ethylene, propylene,1-butene, isobutene and the like and mixtures thereof. The morepreferred source of alkenyl group is from polyisobutene having a gelpermeation chromotography (GPC) number average molecular weight of up to10,000 or higher, preferably in the range of about 500 to about 2,500,and most preferably in the range of about 800 to about 1,500.

Preferred procedures for phosphorylating ashless dispersants include,for example, those described in U.S. Pat. Nos. 6,627,584, 4,857,214, and5,198,133, which descriptions are incorporated herein by reference.

The amount of ashless dispersant on an “active ingredient basis” (i.e.,excluding the weight of impurities, diluents and solvents typicallyassociated therewith) is generally within the range of about 0.5 toabout 7.5 weight percent (wt %), typically within the range of about 0.5to 6.5 wt %, preferably within the range of about 0.5 to about 5.5 wt %,and most preferably within the range of about 1.0 to about 4.5 wt %. Ina preferred embodiment, this dispersant component of the presentinvention is a dispersant having a nitrogen to phosphorus mass ratiobetween about 3:1 and about 10:1. The ashless dispersant of a preferredembodiment can be prepared by phosphorylating the succinimide compoundto such a degree that the resulting nitrogen to phosphorus mass ratio inthe reaction product is between about 3:1 and about 10:1. In anotherembodiment, a phosphorylated dispersant and a non-phosphorylateddispersant are blended together such that the total nitrogen tophosphorus mass ratio of the dispersant is between about 3:1 and about10:1.

The phosphorylated succinimide dispersant compounds of the invention maybe used at a concentration of about 0.01 wt % to about 12 wt %,particularly about 0.01 wt % to about 10 wt %, to insure that thefinished blend contains an adequate quantity of the foregoing ingredientalthough smaller amounts may be successfully employed, depending on therelative amounts of components (A), (B) and (C), and alternatively,larger amounts also may be used so long as the relative amounts ofcomponents (A), (B) and (C) are sufficient to keep ∂μ/∂T negative.

Combined Use of Components (A) (B) (C) and (D)

Anti-NVH characteristics are improved for a power transmission fluidwhich is formulated to predominantly contain base oil, and a minoramount of an additive composition containing 0.002-0.5 wt % alkoxylatedamine (Component (A)), 0.001-0.5 wt % dihydrocarbyl phosphite (Component(B)), 0.01-1.0 wt % metallic detergent (Component (C)), and 0.01-12 wt %phosphorylated succinimide (Component (D)). Particularly, the fluidcomposition may contain about 0.01-0.2 wt % Component (A); 0.01-0.7 wt %Component (B); 0.01-10 wt % Component (C); and 0.01-10 wt % Component(D). Components (A), (B), (C) and (D) may be introduced into a fluidcomposition comprising a major amount of base oil either as an additiveconcentrate, individually, etc. An additive concentrate containing thesecomponents may be incorporated into a finished composition at a treatrate of about 3 wt % to about 20, particularly about 5 wt % to about 15wt %, based on the overall fluid composition.

The combined presence of these four components in properly balancedproportions is necessary to achieve the negative the ∂μ/∂T slopecondition associated with achieving improved anti-NVH properties. In oneembodiment, a fluid composition containing all four Components (A)-(D)is formulated such that the fluid composition such that the fluidcomposition comprises a viscosity at 100° C. of <6 cSt, a viscosity at40° C. of <30 cSt, and a Brookfield Viscosity at −40° C. of <10,000 cP,and wherein the ∂μ/∂T slope value is determined from coefficient offriction and temperature measurements taken on a low speed SAE #2Machine using a paper friction material lined clutch plate and testingconditions of 0.79 N/mm², >50 rpm, and at 40° C. and 120° C. The paperfriction material lining material used in the testing machines may be acommercial product made/supplied by Borg Warner Automotive as BorgWarner 4329. A power transmission fluid including only one, two or threeof components (A)-(D), but not all, or not in balanced proportions, cannot predictably and reliably provide a transmission fluid having anegative ∂μ/∂T.

B. Additive Package II for Enhanced Anti-NVH Durability Performance

Six components, inclusive of the above four-discussed Components (A)-(D)and two additional surfactant compounds, Compounds (E) and (F) describedin more detail below, of an automatic transmission fluid, canadditionally be used for maintaining more stable anti-NVH durability ofthe fluid as it ages over a service life.

Component (E): Tertiary Fatty Amine

Component (E) comprises a tertiary fatty amine surfactant/frictionmodifier which is included in the additive package and transmissionfluids of the present invention. The co-presence of this component. andComponent (F) described below, in a composition containing Components(A)-(D) has been found to help maintain desired friction properties asthe fluid ages over a service life.

The tertiary fatty amine may be represented by the following formula:

wherein R₁ and R₂ can independently represent C₁ to C₆, and R₃ mayrepresent a C₁₀ to C₂₆ alkyl or alkenyl group. Preferred tertiary fattyamines are selected with R₃ representing dialkyl C₁₆-C₂₂ alkylamines inwhich the fatty alkyl chains. Suitable tertiary fatty amines include,for example: dimethyl decylamine, dimethyl laurylamine, dimethylmyristylamine, dimethyl cetylamine, dimethyl stearylamine, dimethylarachadylamine, dimethyl behenylamine, dimethyl cocoylamine, anddimethyl tallowylamine, or combinations thereof. In one preferredembodiment, the long chain tertiary amine comprises dimethylstearyl-amine (N,N-dimethyl 1-octadecamine) which is represented by theformula C₁₈H₃₇N(CH₃)₂.

The tertiary fatty amine compounds of the invention should be used at aconcentration of 0.005 wt % to about 1.0 wt %, particularly about 0.01wt % to about 0.7 wt %, to insure that the finished blend contains anadequate quantity of the foregoing ingredient for anti-NVH durabilityenhancements although smaller amounts may be successfully employed,depending on the relative amounts of components (A)-(D), and (E).

Component (F): Alkoxylated Alcohol

Component (F) comprises an alkoxylated alcohol non-ionic surfactantwhich is included in the additive package and transmission fluids of thepresent invention. The level of this component in the transmission fluidmust be sufficient to maintain friction properties as the fluid agesover a service life.

Alkoxylated alcohols which can be used in forming the additives of thisinvention include, for example, oil-soluble alkoxylated alkanols,alkoxylated cycloalkanols, alkoxylated polyols, alkoxylated phenols, andalkoxylated heterocyclic alcohols which contain an average of up toabout 20 alkoxy groups per molecule. The alkoxy groups can be methoxy,ethoxy, propoxy, butoxy, or pentoxy, or combinations of two or more ofthese. However ethoxy-substituted alcohols are preferred. Thealkoxylated alcohol should be a liquid at ambient temperatures in therange of 20-25° C. Since the alkoxylated alcohol should be oil-soluble,short chain alcohols preferably contain an average of at least twoalkoxy groups per molecule whereas longer chain alcohols may contain oneor more alkoxy groups per molecule. The average number of alkoxy groupsin any given alcohol can be as high as 15 or 20 as long as the productis oil soluble and is preferably a liquid at room temperature. Examplesof alcohols that form suitable alkoxylated alcohols include C₁₋₂₄alkanols, C₁₋₁₀ cycloalkanols, polyols having up to about 16 carbonatoms and 2-5 hydroxyl groups, polyol ethers having up to about 16carbon atoms and at least one hydroxyl group, phenol, alkylphenolshaving up to about 16 carbon atoms, and hydroxy-substituted heterocycliccompounds such as tetrahydrofurfuryl alcohol andtetrahydropyran-2-methanol.

Preferred is an alkoxylated alcohol of 8 to 16 carbon atoms or mixtureof two or more of such alcohols having an average of 1 to 10 ethoxygroups per molecule. Particularly preferred are ethoxylated alcohols,such as an ethoxylated C₁₀₋₁₄ alcohol having an average of 1 to 3 ethoxygroups per molecule.

The alkoxylated alcohol compounds of the invention should be used at aconcentration of 0.01 wt % to about 0.7 wt %, particularly about 0.01 wt% to about 0.5 wt %, to insure that the finished blend contains anadequate quantity of the foregoing ingredient for anti-NVH durabilityenhancements although smaller amounts may be successfully employed,depending on the relative amounts of components (A)-(E).

Combined Use of Components (A)-(F)

Anti-NVH durability characteristics are improved for a powertransmission fluid which is formulated to predominantly contain baseoil, and a minor amount of an additive composition containing 0.002-0.5wt % alkoxylated amine (Component (A)), 0.001-0.5 wt % dihydrocarbylphosphite (Component (B)), 0.01-1.0 wt % metallic detergent (Component(C)), 0.01-12 wt % phosphorylated succinimide (Component (D)), 0.005-10wt % long chain tertiary amine (Component (L)), and 0.01-0.7 ethoxylatedalcohol (Component (F)). Particularly, the fluid composition may containabout 0.01-25 wt % Component (A); 0.01-0.2 wt % Component (B); 0.01-0.7wt % Component (C); 0.01-10 wt % Component (D); 0.01-0.7 wt % Component(L); and 0.01-0.5 wt % Component (F). Components (A), (B), (C), (D), (L)and (F) may be introduced into a fluid composition comprising a majoramount of base oil either as an additive concentrate, individually, etc.An additive concentrate containing these components may be incorporatedinto a finished composition at a treat rate of about 3 wt % to about 20,particularly about 5 wt % to about 15 wt %, based on the overall fluidcomposition.

The combined presence of these six components is necessary to achievemore stable and uniform friction interactions between the fluid andclutch plate as the fluid ages. In one embodiment, a fluid compositioncontaining all six Components (A)-(F) is formulated such that the fluidcomposition comprises a viscosity at 100° C. of <6 cSt, a viscosity at40° C. of <30 cSt, and a Brookfield Viscosity at −40° C. of <10,000 cP,and wherein the fluid has a variation in coefficient of friction attesting rpm ranging from 50 to 300 of less than about 0.015 (absolutevalue) as determined from measurements taken on an SAE #2 Machine usinga test plate comprising a paper friction material lined clutch plate andtesting conditions ranging from about 0.3 to about 3.4 N/mm², such as0.79 N/mm² at 150° C. for 200 hours. In another embodiment, the fluidfurther has quasi-static friction greater than 0.098 and static frictionof 0.123 or greater, as measured on a ZF GK rig. In another embodiment,the fluid has an anti-NVH characteristic having a threshold pressurevalue greater in value than 0.8 N/mm² as measured on a ZF GK rig. Inanother embodiment, the fluid has an NVH characteristic which, afterexposure to oxidizing conditions, does not decrease in value below theinitial value of the NVH characteristic value before the exposure asmeasured on a ZF GK rig. In yet another embodiment, the fluid has an NVHcharacteristic which, after exposure to oxidizing conditions, does notdecrease to a value below the initial value of the NVH characteristicbefore exposure as measured on the ZF GK rig. The “NVH characteristic”refers to noise phenomena, such as squawk, chatter, shudder, and/ornoise. In one non-limiting embodiment, the NVH characteristic is squawk.

A power transmission fluid including less than all six of components(A)-(F) can not predictably and reliably maintain such uniform andstable friction properties at the clutch, e.g., greater variation in thecoefficient of friction parameter may be observed.

Other Optional Additive Components

The fluids of the present embodiments may also optionally includeconventional additives of the type used in power transmission fluidformulations and gear lubricants in addition to the extreme pressure andantiwear performance improving co-additives described above. Suchadditives include, but are not limited to, metallic detergents,dispersants, friction modifiers, antioxidants, viscosity indeximprovers, copper corrosion inhibitors, anti-rust additives, antiwearadditives, antifoamants, pour point depressants, seal swell agents,colorants, metal deactivators, and/or air expulsion additives. It willbe appreciated that various required and optional additives describedherein may have additional other advantageous effects in the finishedfluids.

Component (G): Supplemental Dispersants

Component (G) comprises at least one oil-soluble supplementaldispersant. Suitable dispersants may include ashless dispersants such assuccinic dispersants, Mannich base dispersants, and polymeric polyaminedispersants. Hydrocarbyl-substituted succinic acylating agents are usedto make hydrocarbyl-substituted succinimides. Thehydrocarbyl-substituted succinic acylating agents include, but are notlimited to, hydrocarbyl-substituted succinic acids,hydrocarbyl-substituted succinic anhydrides, the hydrocarbyl-substitutedsuccinic acid halides (especially the acid fluorides and acidchlorides), and the esters of the hydrocarbyl-substituted succinic acidsand lower alcohols (e.g., those containing up to 7 carbon atoms), thatis, hydrocarbyl-substituted compounds which can function as carboxylicacylating agents.

Hydrocarbyl substituted acylating agents are made by reacting apolyalkyl olefin or chlorinated polyalkyl olefin of appropriatemolecular weight with maleic anhydride. Similar carboxylic reactants canbe used to make the acylating agents. Such reactants may include, butare not limited to, maleic acid, fumaric acid, malic acid, tartaricacid, itaconic acid, itaconic anhydride, citraconic acid, citraconicanhydride, mesaconic acid, ethylmaleic anhydride, dimethylmaleicanhydride, ethylmaleic acid, dimethylmaleic acid, hexylmaleic acid, andthe like, including the corresponding acid halides and lower aliphaticesters.

The molecular weight of the olefin can vary depending upon the intendeduse of the substituted succinic anhydrides. Typically, the substitutedsuccinic anhydrides will have a hydrocarbyl group of from about 8 toabout 500 carbon atoms. However, substituted succinic anhydrides used tomake lubricating oil dispersants will typically have a hydrocarbyl groupof about 40 to about 500 carbon atoms. With high molecular weightsubstituted succinic anhydrides, it is more accurate to refer to numberaverage molecular weight (Mn) since the olefins used to make thesesubstituted succinic anhydrides may include a mixture of differentmolecular weight components resulting from the polymerization of lowmolecular weight olefin monomers such as ethylene, propylene, andisobutylene.

The mole ratio of maleic anhydride to olefin can vary widely. It mayvary, for example, from about 5:1 to about 1:5, or for example, fromabout 1:1 to about 3:1. With olefins such as polyisobutylene having anumber average molecular weight of about 500 to about 7000, or as afurther example, about 800 to about 3000 or higher and theethylene-alpha-olefin copolymers, the maleic anhydride may be used instoichiometric excess, e.g. about 1.1 to about 3 moles maleic anhydrideper mole of olefin. The unreacted maleic anhydride can be vaporized fromthe resultant reaction mixture.

The polyalkyl or polyalkenyl substituent on the succinic anhydridesemployed herein is generally derived from polyolefins, which arepolymers or copolymers of mono-olefins, particularly 1-mono-olefins,such as ethylene, propylene, and butylene. The mono-olefin employed mayhave about 2 to about 24 carbon atoms, or as a further example, about 3to about 12 carbon atoms. Other suitable mono-olefins include propylene,butylene, particularly isobutylene, 1-octene, and 1-decene. Polyolefinsprepared from such mono-olefins include polypropylene, polybutene,polyisobutene, and the polyalphaolefins produced from 1-octene and1-decene.

Polyalkenyl succinic anhydrides may be converted to polyalkyl succinicanhydrides by using conventional reducing conditions such as catalytichydrogenation. For catalytic hydrogenation, a suitable catalyst ispalladium on carbon. Likewise, polyalkenyl succinimides may be convertedto polyalkyl succinimides using similar reducing conditions.

In some embodiments, the ashless dispersant may include one or morealkenyl succinimides of an amine having at least one primary amino groupcapable of forming an imide group. The alkenyl succinimides may beformed by conventional methods such as by heating an alkenyl succinicanhydride, acid, acid-ester, acid halide, or lower alkyl ester with anamine containing at least one primary amino group. The alkenyl succinicanhydride may be made readily by heating a mixture of polyolefin andmaleic anhydride to about 180°-220° C. The polyolefin may be a polymeror copolymer of a lower monoolefin such as ethylene, propylene,isobutene and the like, having a number average molecular weight in therange of about 300 to about 3000 as determined by gel permeationchromatography (GPC).

Amines which may be employed in forming the ashless dispersant includeany that have at least one primary amino group which can react to forman imide group and at least one additional primary or secondary aminogroup and/or at least one hydroxyl group. A few representative examplesare: N-methyl-propanediamine, N-dodecylpropanediamine,N-aminopropyl-piperazine, ethanolamine, N-ethanol-ethylenediamine, andthe like.

Suitable amines may include polyalkylene polyamines, such as propylenediamine, dipropylene triamine, di-(1,2-butylene)triamine, andtetra-(1,2-propylene)pentamine. A further example includes thepolyethylene polyamines which can be depicted by the formulaH₂N(CH₂CH₂NH)_(n)H, wherein n may be an integer from about one to aboutten. These include: ethylene diamine, diethylene triamine (DETA),triethylene tetramine (TETA), tetraethylene pentamine (TEPA),pentaethylene hexamine (PEHA), and the like, including mixtures thereofin which case n is the average value of the mixture. Such polyethylenepolyamines have a primary amine group at each end so they may formmono-alkenylsuccinimides and bis-alkenylsuccinimides. Commerciallyavailable polyethylene polyamine mixtures may contain minor amounts ofbranched species and cyclic species such as N-aminoethyl piperazine,N,N′-bis(aminoethyl)piperazine, N,N′-bis(piperazinyl)ethane, and likecompounds. The commercial mixtures may have approximate overallcompositions falling in the range corresponding to diethylene triamineto tetraethylene pentamine. The molar ratio of polyalkenyl succinicanhydride to polyalkylene polyamines may be from about 1:1 to about3.0:1.

In some embodiments, the ashless dispersant may include the products ofthe reaction of a polyethylene polyamine, e.g. triethylene tetramine ortetraethylene pentamine, with a hydrocarbon substituted carboxylic acidor anhydride made by reaction of a polyolefin, such as polyisobutene, ofsuitable molecular weight, with an unsaturated polycarboxylic acid oranhydride, e.g., maleic anhydride, maleic acid, fumaric acid, or thelike, including mixtures of two or more such substances.

Polyamines that are also suitable in preparing the dispersants describedherein include N-arylphenylenediamines, such asN-phenylphenylenediamines, for example, N-phenyl-1,4-phenylenediamine,N-phenyl-1,3-phenylenediamine, and N-phenyl-1,2-phenylenediamine;aminothiazoles such as aminothiazole, aminobenzothiazole,aminobenzothiadiazole, and aminoalkylthiazole; aminocarbazoles;aminoindoles; aminopyrroles; amino-indazolinones;aminomercaptotriazoles; aminoperimidines; aminoalkyl imidazoles, such as1-(2-aminoethyl)imidazole, 1-(3-aminopropyl)imidazole; and aminoalkylmorpholines, such as 4-(3-aminopropyl)morpholine. These polyamines aredescribed in more detail in U.S. Pat. Nos. 4,863,623 and 5,075,383. Suchpolyamines can provide additional benefits, such as anti-wear andantioxidancy, to the final products.

Additional polyamines useful in forming the hydrocarbyl-substitutedsuccinimides include polyamines having at least one primary or secondaryamino group and at least one tertiary amino group in the molecule astaught in U.S. Pat. Nos. 5,634,951 and 5,725,612. Examples of suitablepolyamines include N,N,N″,N″-tetraalkyldialkylenetriamines (two terminaltertiary amino groups and one central secondary amino group),N,N,N′,N″-tetraalkyltrialkylenetetramines (one terminal tertiary aminogroup, two internal tertiary amino groups and one terminal primary aminogroup), N,N,N′,N″,N′″-pentaalkyltrialkylenetetramines (one terminaltertiary amino group, two internal tertiary amino groups and oneterminal secondary amino group),tris(dialkylaminoalkyl)-aminoalkylmethanes (three terminal tertiaryamino groups and one terminal primary amino group), and like compounds,wherein the alkyl groups are the same or different and typically containno more than about 12 carbon atoms each, and which may contain fromabout 1 to about 4 carbon atoms each. As a further example, these alkylgroups may be methyl and/or ethyl groups. Polyamine reactants of thistype may include dimethylaminopropylamine (DMAPA) and N-methylpiperazine.

Hydroxyamines suitable for herein include compounds, oligomers orpolymers containing at least one primary or secondary amine capable ofreacting with the hydrocarbyl-substituted succinic acid or anhydride.Examples of hydroxyamines suitable for use herein includeaminoethylethanolamine (AEEA), aminopropyldiethanolamine (APDEA),ethanolamine, diethanolamine (DEA), partially propoxylated hexamethylenediamine (for example HMDA-2PO or HMDA-3PO), 3-amino-1,2-propanediol,tris(hydroxymethyl)aminomethane, and 2-amino-1,3-propanediol.

The mole ratio of amine to hydrocarbyl-substituted succinic acid oranhydride may range from about 1:1 to about 3.0:1. Another example of amole ratio of amine to hydrocarbyl-substituted succinic acid oranhydride may range from about 1.5:1 to about 2.0:1.

The foregoing dispersant may also be a post-treated dispersant made, forexample, by treating the dispersant with maleic anhydride and boric acidas described, for example, in U.S. Pat. No. 5,789,353, or by treatingthe dispersant with nonylphenol, formaldehyde and glycolic acid asdescribed, for example, in U.S. Pat. No. 5,137,980.

The Mannich base dispersants may be a reaction product of an alkylphenol, typically having a long chain alkyl substituent on the ring,with one or more aliphatic aldehydes containing from about 1 to about 7carbon atoms (especially formaldehyde and derivatives thereof), andpolyamines (especially polyalkylene polyamines). For example, a Mannichbase ashless dispersants may be formed by condensing about one molarproportion of long chain hydrocarbon-substituted phenol with from about1 to about 2.5 moles of formaldehyde and from about 0.5 to about 2 molesof polyalkylene polyamine.

Hydrocarbon sources for preparation of the Mannich polyamine dispersantsmay be those derived from substantially saturated petroleum fractionsand olefin polymers, such as polymers of mono-olefins having from about2 to about 6 carbon atoms. The hydrocarbon source generally contains,for example, at least about 40 carbon atoms, and as a further example,at least about 50 carbon atoms to provide substantial oil solubility tothe dispersant. The olefin polymers having a GPC number averagemolecular weight between about 600 and about 5,000 are suitable forreasons of easy reactivity and low cost. However, polymers of highermolecular weight can also be used. Especially suitable hydrocarbonsources are isobutylene polymers and polymers made from a mixture ofisobutene and a raffinate I stream.

Suitable Mannich base dispersants may be Mannich base ashlessdispersants formed by condensing about one molar proportion of longchain hydrocarbon-substituted phenol with from about 1 to about 2.5moles of formaldehyde and from about 0.5 to about 2 moles ofpolyalkylene polyamine.

Polymeric polyamine dispersants suitable as the ashless dispersants arepolymers containing basic amine groups and oil solubilizing groups (forexample, pendant alkyl groups having at least about 8 carbon atoms).Such materials are illustrated by interpolymers formed from variousmonomers such as decyl methacrylate, vinyl decyl ether or relativelyhigh molecular weight olefins, with aminoalkyl acrylates and aminoalkylacrylamides. Examples of polymeric polyamine dispersants are set forth,for example, in U.S. Pat. Nos. 3,687,849 and 3,702,300. Polymericpolyamines may include hydrocarbyl polyamines wherein the hydrocarbylgroup is composed of the polymerization product of isobutene and araffinate I stream as described above. PIB-amines and PIB-polyamines mayalso be used.

Methods for the production of ashless dispersants as described above areknown to those skilled in the art and are reported in the patentliterature. For example, the synthesis of various ashless dispersants ofthe foregoing types is described in such patents as U.S. Pat. Nos.5,137,980 and Re 26,433, herein incorporated by reference.

An example of a suitable ashless dispersant is a borated dispersant.Borated dispersants may be formed by boronating (borating) an ashlessdispersant having basic nitrogen and/or at least one hydroxyl group inthe molecule, such as a succinimide dispersant, succinamide dispersant,succinic ester dispersant, succinic ester-amide dispersant, Mannich basedispersant, or hydrocarbyl amine or polyamine dispersant. Methods thatcan be used for boronating the various types of ashless dispersantsdescribed above are described, for example, in U.S. Pat. Nos. 4,455,243and 4,652,387.

The borated dispersant may include a high molecular weight dispersanttreated with boron such that the borated dispersant includes up to about2 wt % of boron. As another example the borated dispersant may includefrom about 0.8 wt % or less of boron. As a further example, the borateddispersant may include from about 0.1 to about 0.7 wt % of boron. As aneven further example, the borated dispersant may include from about 0.25to about 0.7 wt % of boron. As a further example, the borated dispersantmay include from about 0.35 to about 0.7 wt % of boron. The borateddispersant may further include a mixture of borated dispersants. As afurther example, the borated dispersant may include anitrogen-containing dispersant and/or may be free of phosphorus. As anadditional example, the borated dispersant may include phosphorus. Thedispersant may be dissolved in oil of suitable viscosity for ease ofhandling. It should be understood that the weight percentages given hereare for neat dispersant, without any diluent oil added.

A dispersant may be further reacted with an organic acid, an anhydride,and/or an aldehyde/phenol mixture. Such a process may enhancecompatibility with elastomer seals, for example.

A dispersant may be present in the power transmission fluid in an amountof up to about 15 wt %. Further, the fluid composition may include fromabout 0.1 wt % to about 10 wt % of the borated dispersant. Further, thefluid composition may include from about 3 wt % to about 5 wt % of theborated dispersant. Further, the power transmission fluid may include anamount of the borated dispersant sufficient to provide up to 1900 partsper million (ppm) by weight of boron in the finished fluid, such as forexample, from about 50 to about 500 ppm by weight of boron in thefinished fluid.

Component (H): Lubricity Antiwear and Extreme Pressure Agents

Lubricity, antiwear and extreme pressure agents may be included.Examples of these include sulfur sources such as sulfurized fatty oils.“Sulfurized fatty oil” refers to sulfurized fatty acids, sulfurizedfatty esters, individually or as mixtures thereof. Sulfurized fatty acidesters are preferred. The sulfurized fatty oils may be animal orvegetable in origin. Suitable sulfurized fatty oils include, forexample, a sulfurized fatty acid ester containing about 10% sulfur and asulfurized sperm oil containing about 10% sulfur.

In one particular embodiment, suitable sulfurized fatty oils includesulfurized transesterified triglycerides, such as those described inU.S. Pat. No. 4,380,499, which descriptions are incorporated herein byreference. In one embodiment, a sulfurized transesterified triglycerideadditive has a total acid component comprising no less than about 35 mol% saturated aliphatic acids and no more than about 65 mol % unsaturatedfatty acids, and wherein the total acid component is furthercharacterized as comprising more than about 20 mol % of monounsaturatedacids, less than about 15 mol % of polyunsaturated fatty acids, morethan about 20 mol % saturated aliphatic acids having 6 to 16 carbonatoms, including more than about 10 mol % saturated aliphatic acidshaving 6 to 14 carbon atoms, and less than about 15 mol % saturatedaliphatic acids having 18 or more carbon atoms. Suitable sulfurizedfatty oils also include those such as those described in U.S. Pat. No.4,149,982, which descriptions are incorporated herein by reference.

Other suitable sulfurized fatty oils include, for example, sulfurizedlard oils, sulfurized fatty compounds, sulfurized methyl esters,sulfurized hydrocarbons, sulfurized oleic acid, sulfurized fattyester-polyalkanol amides, and sulfurized fatty olefins.

Other antiwear agents include phosphorus-containing antiwear agents,such as those comprising an organic ester of phosphoric acid,phosphorous acid, or an amine salt thereof.

The phosphorus-containing antiwear agent may be present in an amountsufficient to provide about 50 to about 500 parts per million by weightof phosphorus in the power transmission fluid. As a further example, thephosphorus-containing antiwear agent may be present in an amountsufficient to provide about 150 to about 300 parts per million by weightof phosphorus in the power transmission fluid.

The fluid composition may include up to about 1.0 wt % of thephosphorus-containing antiwear agent. As a further example, the fluidcomposition may include from about 0.01 wt % to about 1.0 wt % of thephosphorus-containing antiwear agent, particularly about 0.2 wt % toabout 0.3 wt % of the phosphorus-containing antiwear agent.

Component (I): Metal Deactivators

The formulations also may contain metal deactivators, which includematerials commonly used for that purpose in this general class offluids. These may comprise, for example, ashless dialkyl thiadiazoles.Dialkyl thiadiazoles suitable for the practice of the present inventionmay be of the general formula (I):

wherein R₁ and R₂ may be the same or different hydrocarbyl groups, and xand y independently may be integers from 0 to 8. In one aspect, R₁ andR₂ may be the same or different, linear, branched, or aromatic,saturated or unsaturated hydrocarbyl group having from about 6 to about18 carbon atoms, particularly from about 8 to about 12 carbon atoms, andx and y each may be 0 or 1.

An suitable dialkyl thiadiazoles includes2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazoles. Examples of othersuitable dialkyl thiadiazoles include, for example,2,5-bis(hydrocarbylthio)-1,3,4-thiadiazoles,2-(tert-hydrocarbyldithio)-5-mercapto-1,3,4-thiadiazoles, andbis-tert-dodecylthiothiadiazole.

Suitable dialkyl thiadiazoles also include those such as described, forexample, in U.S. Pat. Nos. 4,149,982 and 4,591,645, and whichdescriptions are incorporated herein by reference. Mixtures of dialkylthiadiazoles of formula (I) with monoalkyl thiadiazoles may also be usedwithin the scope of the present invention.

As used herein, the term “hydrocarbyl group” or “hydrocarbyl” is used inits ordinary sense, which is well-known to those skilled in the art.Specifically, it refers to a group having a carbon atom directlyattached to the remainder of a molecule and having a predominantlyhydrocarbon character. Examples of hydrocarbyl groups include:

(1) hydrocarbon substituents, that is, aliphatic (e.g., alkyl oralkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, andaromatic-, aliphatic-, and alicyclic-substituted aromatic substituents,as well as cyclic substituents wherein the ring is completed throughanother portion of the molecule (e.g., two substituents together form analicyclic radical);

(2) substituted hydrocarbon substituents, that is, substituentscontaining non-hydrocarbon groups which, in the context of thedescription herein, do not alter the predominantly hydrocarbonsubstituent (e.g., halo (especially chloro and fluoro), hydroxy, alkoxy,mercapto, alkylmercapto, nitro, nitroso, and sulfoxy);

(3) hetero-substituents, that is, substituents which, while having apredominantly hydrocarbon character, in the context of this description,contain other than carbon in a ring or chain otherwise composed ofcarbon atoms. Hetero-atoms include sulfur, oxygen, nitrogen, andencompass substituents such as pyridyl, furyl, thienyl, and imidazolyl.In general, no more than two, or as a further example, no more than one,non-hydrocarbon substituent will be present for every ten carbon atomsin the hydrocarbyl group; typically, there will be no non-hydrocarbonsubstituent in the hydrocarbyl group.

The fluid composition may include up to about 2.0 wt % of the metaldeactivators.

Component (J): Supplemental Friction Modifiers

Supplemental friction modifiers optionally are used in automatictransmission fluids to help decrease friction between surfaces (e.g.,the members of a torque converter clutch or a shifting clutch) at lowsliding speeds. The result is a friction-vs.-velocity (μ-v) curve thathas a positive slope, which in turn leads to smooth clutch engagementsand minimizes “stick-slip” behavior (e.g., shudder, noise, and harshshifts).

Friction modifiers include such compounds as aliphatic amines orethoxylated aliphatic amines, ether amines, alkoxylated ether amines,aliphatic fatty acid amides, acylated amines, aliphatic carboxylicacids, aliphatic carboxylic esters, polyol esters, aliphatic carboxylicester-amides, imidazolines, tertiary amines, aliphatic phosphonates,aliphatic phosphates, aliphatic thiophosphonates, aliphaticthiophosphates, etc., wherein the aliphatic group usually contains oneor more carbon atoms so as to render the compound suitably oil soluble.As a further example, the aliphatic group may contain about 8 or morecarbon atoms.

One group of friction modifiers includes the N-aliphatichydrocarbyl-substituted diethanol amines in which the N-aliphatichydrocarbyl-substituent is at least one straight chain aliphatichydrocarbyl group free of acetylenic unsaturation and having in therange of about 14 to about 20 carbon atoms.

An example of a suitable friction modifier system is composed of acombination of at least one N-aliphatic hydrocarbyl-substituteddiethanol amine and at least one N-aliphatic hydrocarbyl-substitutedtrimethylene diamine in which the N-aliphatic hydrocarbyl-substituent isat least one straight chain aliphatic hydrocarbyl group free ofacetylenic unsaturation and having in the range of about 14 to about 20carbon atoms. Further details concerning this friction modifier systemare set forth in U.S. Pat. Nos. 5,372,735 and 5,441,656.

Another friction modifier system is based on the combination of (i) atleast one di(hydroxyalkyl)aliphatic tertiary amine in which thehydroxyalkyl groups, being the same or different, each contain fromabout 2 to about 4 carbon atoms, and in which the aliphatic group is anacyclic hydrocarbyl group containing from about 10 to about 25 carbonatoms, and (ii) at least one hydroxyalkyl aliphatic imidazoline in whichthe hydroxyalkyl group contains from about 2 to about 4 carbon atoms,and in which the aliphatic group is an acyclic hydrocarbyl groupcontaining from about 10 to about 25 carbon atoms. For further detailsconcerning this friction modifier system, reference should be had toU.S. Pat. No. 5,344,579.

Another suitable group of friction modifiers include polyolesters, forexample, glycerol monooleate (GMO), glycerol monolaurate (GML), and thelike.

Generally speaking, the fluid compositions may contain up to about 1.25wt %, or, as a further example, from about 0.05 to about 1 wt % of oneor more friction modifiers.

Component (K): Antioxidants

In some embodiments, antioxidant compounds may be included in thecompositions. Antioxidants include phenolic antioxidants, aromatic amineantioxidants, sulfurized phenolic antioxidants, and organic phosphites,among others. Examples of phenolic antioxidants include2,6-di-tert-butylphenol, liquid mixtures of tertiary butylated phenols,2,6-di-tert-butyl-4-methylphenol,4,4′-methylenebis(2,6-di-tert-butylphenol),2,2′-methylenebis(4-methyl6-tert-butylphenol),mixed methylene-bridged polyalkyl phenols, and4,4′-thiobis(2-methyl-6-tert-butylphenol).N,N′-di-sec-butyl-phenylenediamine, 4-isopropylaminodiphenylamine,phenyl-.alpha.-naphthyl amine, phenyl-.alpha.-naphthyl amine, andring-alkylated diphenylamines. Examples include the sterically hinderedtertiary butylated phenols, bisphenols and cinnamic acid derivatives andcombinations thereof. The amount of antioxidant in the fluidcompositions described herein may include up to about 5 wt % based onthe total weight of the fluid formulation. It may range particularlyfrom about 0.01 to about 3.0 wt %, more particularly from about 0.1 wt %to about 0.7 wt %, based on the total weight of the fluid formulation.

Component (L): Anti-Rust Agents

Rust or corrosion inhibitors are another type of inhibitor additive foruse in embodiments of the present disclosure. Such materials includemonocarboxylic acids and polycarboxylic acids. Examples of suitablemonocarboxylic acids are octanoic acid, decanoic acid and dodecanoicacid. Suitable polycarboxylic acids include dimer and trimer acids suchas are produced from such acids as tall oil fatty acids, oleic acid,linoleic acid, or the like. Another useful type of rust inhibitor maycomprise alkenyl succinic acid and alkenyl succinic anhydride corrosioninhibitors such as, for example, tetrapropenylsuccinic acid,tetrapropenylsuccinic anhydride, tetradecenylsuccinic acid,tetradecenylsuccinic anhydride, hexadecenylsuccinic acid,hexadecenylsuccinic anhydride, and the like. Also useful are the halfesters of alkenyl succinic acids having about 8 to about 24 carbon atomsin the alkenyl group with alcohols such as the polyglycols. Othersuitable rust or corrosion inhibitors include ether amines; acidphosphates; amines; polyethoxylated compounds such as ethoxylatedamines, ethoxylated phenols, and ethoxylated alcohols; imidazolines;aminosuccinic acids or derivatives thereof, and the like. Materials ofthese types are commercially available. Mixtures of such rust orcorrosion inhibitors can be used. The amount of corrosion inhibitor inthe fluid compositions described herein may include up to about 2.0 wt %based on the total weight of the composition. It may range particularlyfrom about 0.01 to about 2.0 wt %, more particularly from about 0.01 toabout 0.3 wt %, based on the total weight of the formulation.

Component (M): Copper Corrosion Inhibitors

In some embodiments, copper corrosion inhibitors may constitute anotherclass of additives suitable for inclusion in the compositions. Suchcompounds include thiazoles, triazoles, and thiadiazoles. Examples ofsuch compounds include benzotriazole, tolyltriazole, octyltriazole,decyltriazole, dodecyltriazole, 2-mercapto benzothiazole,2,5-dimercapto-1,3,4-thiadiazole,2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazoles,2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazoles,2,5-bis(hydrocarbylthio)-1,3,4-thiadiazoles, and2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazoles. Suitable compoundsinclude the 1,3,4-thiadiazoles, a number of which are available asarticles of commerce, and also combinations of triazoles such astolyltriazole with a 1,3,5-thiadiazole such as a2,5-bis(alkyldithio)-1,3,4-thiadiazole. Regarding dialkyl thiadiazoles,for imparting corrosion inhibition, that additive previously has beenused in much smaller treat levels than the levels used in the presentinvention to enhance extreme pressure and antiwear properties (when usedin combination with relatively high levels of sulfurized fatty oil asindicated herein). The 1,3,4-thiadiazoles are generally synthesized fromhydrazine and carbon disulfide by known procedures. See, for example,U.S. Pat. Nos. 3,862,798 and 3,840,549.

The amount of the corrosion inhibitor in the fluid compositionsdescribed herein may include up to about 1.0 wt % based on the totalweight of the composition.

Component (N): Viscosity Index Improvers

Viscosity index improvers for use in the above described fluidcompositions and gear lubricant compositions may be selected frompolyisoalkylene compounds, polymethacrylate compounds, and anyconventional viscosity index improvers. An example of a suitablepolyisoalkylene compound for use as a viscosity index improver includespolyisobutylene having a weight average molecular weight ranging fromabout 700 to about 2,500. Embodiments may include a mixture of one ormore viscosity index improvers of the same or different molecularweight.

Suitable viscosity index improvers may include styrene-maleic esters,polyalkylmethacrylates, and olefin copolymer viscosity index improvers.Mixtures of the foregoing products can also be used as well asdispersant and dispersant-antioxidant viscosity index improvers.

The fluid composition may include up to about 25 wt % based of aviscosity index improver. It may contain viscosity index improver in anamount ranging particularly from about 0.1 to about 25 wt %, based onthe total weight of the formulation.

Component (O): Antifoam Agents

In some embodiments, a foam inhibitor may form another componentsuitable for use in the compositions. Foam inhibitors may be selectedfrom silicones, polyacrylates, surfactants, and the like. The amount ofantifoam agent in the fluid compositions described herein may include upto about 0.5 wt % based on the total weight of the composition. It mayrange particularly from about 0.01 to about 0.5 wt %, more particularlyfrom about 0.01 to about 0.1 wt %, based on the total weight of theformulation.

Component (P): Seal Swell Agents

The seal swell agent used in the transmission fluid compositionsdescribed herein is selected from oil-soluble diesters, oil-solublesulfones, and mixtures thereof. Generally speaking the most suitablediesters include the adipates, azelates, and sebacates of C₈-C₁₃alkanols (or mixtures thereof), and the phthalates of C₄-C₁₃ alkanols(or mixtures thereof). Mixtures of two or more different types ofdiesters (e.g., dialkyl adipates and dialkyl azelates, etc.) can also beused. Examples of such materials include the n-octyl, 2-ethylhexyl,isodecyl, and tridecyl diesters of adipic acid, azelaic acid, andsebacic acid, and the n-butyl, isobutyl, pentyl, hexyl, heptyl, octyl,nonyl, decyl, undecyl, dodecyl, and tridecyl diesters of phthalic acid.

Other esters which may give generally equivalent performance are polyolesters. Suitable sulfone seal swell agents are described in U.S. Pat.Nos. 3,974,081 and 4,029,587. Typically these products are employed atlevels in the range of up to about 30 wt %. The amount of seal swellagent in the fluid compositions described herein may range particularlyfrom about 1 to about 15 wt %, particularly from about 0.25 wt % toabout 1 wt %, in the finished fluid.

Suitable seal swell agents are the oil-soluble dialkyl esters of (i)adipic acid, (ii) sebacic acid, or (iii) phthalic acid. The adipates andsebacates may be used in amounts in the range of up to about 30 wt %.These amounts may range particularly from about 1 to about 15 wt %, moreparticularly from about 1.5 to about 10 wt %, in the finished fluid. Inthe case of the phthalates, the levels in the fluid may fall in therange of from about 1.5 to about 15 wt %.

Component (Q): Dye:

A colorant may be added to the fluid to give it a detectable character.Generally, azo class dyes are used, such as C.I. Solvent Red 24 or C.I.Solvent Red 164, as set forth in the “Color Index” of the AmericanAssociation of textile Chemists and Colorists and the Society of Dyersand Colourists (U.K.). For automatic transmission fluids, Automatic RedDye is preferred. Dye may be present in a very minimal amount, such asup to about 400 ppm, and particularly ranging from about 200 to about300 ppm in the finished fluid.

Component (R): Diluent

If the additives are provided in an additive package concentrate, asuitable carrier diluent is added to ease blending, solubilizing, andtransporting the additive package. The diluent oil needs to becompatible with the base oil and the additive package. In oneembodiment, the diluent is present in the concentrate in an amount ofbetween about 5 to about 20%, although it can vary widely withapplication. Generally speaking, less diluent is preferable as it lowerstransportation costs and treat rates.

Additives used in formulating the compositions described herein can beblended into base oil individually or in various sub-combinations.However, it is suitable to blend all of the components concurrentlyusing an additive concentrate (i.e., additives plus a diluent, such as ahydrocarbon solvent). The use of an additive concentrate takes advantageof the mutual compatibility afforded by the combination of ingredientswhen in the form of an additive concentrate. Also, the use of aconcentrate reduces blending time and lessens the possibility ofblending errors.

Fluid compositions described herein may include diluent in an amount ofup to about 25 wt % based on the total weight of the finished fluid.

Base Oil

Transmission fluids of the present invention typically (but notnecessarily always) are formulated with a major amount of a base oil anda minor amount of the additive package which includes theextreme-pressure/antiwear enhancing combination of sulfurized fatty oiland dialkyl thiadiazole at the prescribed addition levels. In oneembodiment, a power transmission fluid composition is formulated tocontain a major amount of base oil and about 3 wt % to about 20 wt %,particularly about 5 wt % to about 13 wt %, of an additive compositioncontaining the sulfurized fatty oil and dialkyl thiadiazole in therespective levels prescribed herein.

Base oils suitable for use in formulating fluid compositions accordingto the present disclosure may be selected from any of the synthetic ornatural oils or mixtures thereof. Natural oils include animal oils andvegetable oils (e.g., castor oil, lard oil) as well as minerallubricating oils such as liquid petroleum oils and solvent treated oracid-treated mineral lubricating oils of the paraffinic, naphthenic ormixed paraffinic-naphthenic types. Oils derived from coal or shale arealso suitable. The base oil typically has a viscosity of, for example,from about 2 to about 15 cSt and, as a further example, from about 2 toabout 10 cSt at 100° C. Further, oils derived from a gas-to-liquidprocess are also suitable.

Synthetic oils include hydrocarbon oils such as polymerized andinterpolymerized olefins (e.g., polybutylenes, polypropylenes, propyleneisobutylene copolymers, etc.); polyalphaolefins such as poly(1-hexenes),poly-(1-octenes), poly(1-decenes), etc. and mixtures thereof,alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes,di-nonylbenzenes, di-(2-ethylhexyl)benzenes, etc.); polyphenyls (e.g.,biphenyls, terphenyl, alkylated polyphenyls, etc.); alkylated diphenylethers and alkylated diphenyl sulfides and the derivatives, analogs andhomologs thereof and the like.

Alkylene oxide polymers and interpolymers and derivatives thereof wherethe terminal hydroxyl groups have been modified by esterification,etherification, etc., constitute another class of known synthetic oilsthat may be used. Such oils are exemplified by the oils prepared throughpolymerization of ethylene oxide or propylene oxide, the alkyl and arylethers of these polyoxyalkylene polymers (e.g., methyl-polyisopropyleneglycol ether having an average molecular weight of about 1000, diphenylether of polyethylene glycol having a molecular weight of about500-1000, diethyl ether of polypropylene glycol having a molecularweight of about 1000-1500, etc.) or mono- and polycarboxylic estersthereof, for example, the acetic acid esters, mixed C₃₋₈ fatty acidesters, or the C₁₃ Oxo acid diester of tetraethylene glycol.

Another class of synthetic oils that may be used includes the esters ofdicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinicacids, alkenyl succinic acids, maleic acid, azelaic acid, suberic acid,sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonicacid, alkyl malonic acids, alkenyl malonic acids, etc.) with a varietyof alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol,2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether,propylene glycol, etc.) Specific examples of these esters includedibutyl adipate, di(2-ethylhexyl)sebacate, di-n-hexyl fumarate, dioctylsebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate,didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester oflinoleic acid dimer, the complex ester formed by reacting one mole ofsebacic acid with two moles of tetraethylene glycol and two moles of2-ethylhexanoic acid and the like.

Esters useful as synthetic oils also include those made from C₅ to C₁₂monocarboxylic acids and polyols and polyol ethers such as neopentylglycol, trimethylol propane, pentaerythritol, dipentaerythritol,tripentaerythritol, etc.

Hence, the base oil used which may be used to make the transmissionfluid compositions as described herein may be selected from any of thebase oils in Groups I-V as specified in the American Petroleum Institute(API) Base Oil Interchangeability Guidelines.

Such base oil groups are as follows (Table B): TABLE B Base Oil SulfurSaturates Viscosity Group¹ (wt %) (wt %) Index Group I >0.03 and/or <9080 to 120 Group II ≦0.03 And ≧90 80 to 120 Group III ≦0.03 And ≧90 ≧120Group IV all polyalphaolefins (PAOs) Group V all others not included inGroups I-IV¹Groups I-III are mineral oil base stocks.

As set forth above, the base oil may be a poly-alpha-olefin (PAO).Typically, the poly-alpha-olefins are derived from monomers having fromabout 4 to about 30, or from about 4 to about 20, or from about 6 toabout 16 carbon atoms. Examples of useful PAOs include those derivedfrom octene, decene, mixtures thereof, and the like. PAOs may have aviscosity of from about 2 to about 15, or from about 3 to about 12, orfrom about 4 to about 8 cSt at 100° C. Examples of PAOs include 4 cSt at100° C. poly-alpha-olefins, 6 cSt at 100° C. poly-alpha-olefins, andmixtures thereof. Mixtures of mineral oil with the foregoingpoly-alpha-olefins may be used.

The base oil may be an oil derived from Fischer-Tropsch synthesizedhydrocarbons. Fischer-Tropsch synthesized hydrocarbons are made fromsynthesis gas containing H₂ and CO using a Fischer-Tropsch catalyst.Such hydrocarbons typically require further processing in order to beuseful as the base oil. For example, the hydrocarbons may behydroisomerized using processes disclosed in U.S. Pat. No. 6,103,099 or6,180,575; hydrocracked and hydroisomerized using processes disclosed inU.S. Pat. No. 4,943,672 or 6,096,940; dewaxed using processes disclosedin U.S. Pat. No. 5,882,505; or hydroisomerized and dewaxed usingprocesses disclosed in U.S. Pat. Nos. 6,013,171; 6,080,301; or6,165,949.

Unrefined, refined and rerefined oils, either natural or synthetic (aswell as mixtures of two or more of any of these) of the type disclosedhereinabove can be used in the base oils. Unrefined oils are thoseobtained directly from a natural or synthetic source without furtherpurification treatment. For example, a shale oil obtained directly fromretorting operations, a petroleum oil obtained directly from primarydistillation or ester oil obtained directly from an esterificationprocess and used without further treatment would be an unrefined oil.Refined oils are similar to the unrefined oils except they have beenfurther treated in one or more purification steps to improve one or moreproperties. Many such purification techniques are known to those skilledin the art such as solvent extraction, secondary distillation, acid orbase extraction, filtration, percolation, etc. Rerefined oils areobtained by processes similar to those used to obtain refined oilsapplied to refined oils which have been already used in service. Suchrerefined oils are also known as reclaimed or reprocessed oils and oftenare additionally processed by techniques directed to removal of spentadditives, contaminants, and oil breakdown products.

In selecting any of the foregoing optional additives, it is important toensure that the selected component(s) is/are soluble or stablydispersible in the additive package and finished ATF composition, arecompatible with the other components of the composition, and do notinterfere significantly with the performance properties of thecomposition, such as the anti-NVH, anti-NVH durability, extremepressure, antiwear, friction, viscosity and/or shear stabilityproperties, needed or desired, as applicable, in the overall finishedcomposition.

In general, the ancillary additive components are employed in the oilsin minor amounts sufficient to improve the performance characteristicsand properties of the base fluid. The amounts will thus vary inaccordance with such factors as the viscosity characteristics of thebase fluid employed, the viscosity characteristics desired in thefinished fluid, the service conditions for which the finished fluid isintended, and the performance characteristics desired in the finishedfluid.

However, generally speaking, and referring to Table C below, thefollowing general concentrations (weight percent unless otherwiseindicated) of the optional additional components in the base fluids areillustrative: TABLE C Optional Additive Component Range G 0.0-15.00 H0.0-1.00 I 0.0-2.00 J 0.0-1.25 K 0.0-5.00 L 0.0-2.0 M 0.0-1.0 N 0.0-25.0O 0.0-0.5 P 0.0-30.0 Q 0.0-400 ppm R 0.0-25.0 (in concentrate balance)

An exemplary, non-limiting fully formulated fluid compositions forproviding improved NVH suppression and/or anti-NVH durability accordingto embodiments herein are set forth in Table D below. Referencedcomponents correspond to previously identified classes of components.Key components, viz., Components (A)-(D) in the case of NVH suppression,and Components (A)-(F) in the case of anti-NVH durability improvements,within this formulation will be balanced pursuant to guidance providedelsewhere herein within the respective prescribed range amounts. TABLE DGeneral Range Preferred Range Component Amount, wt % Amount, wt %Friction Modifier 0.002-0.25   0.002-0.25 (Component (A)) FrictionModifier 0.01-0.2   0.01-0.2 (Component (B)) Metallic Detergent0.01-0.6   0.01-0.6 (Component (C)) Dispersant 0.01-10    0.01-10 (Component (D)) Surfactant/Friction  0-0.40  0.01-0.40 Modifier(Component (E)) Non-ionic Surfactant 0-0.5 0.01-0.5 (Component ((F)Antioxidants 0.1-0.7    0.1-0.5 Sulfur Source 0.05-1.5   0.05-1.5Thiadiazole 0-2.0   0-2.0 Rust Inhibitors 0-0.3   0-0.2 Antifoam Agents0-0.5   0-0.5 Diluent Oil 0-25   0-25 Basestock 60-95    60-95

It will be appreciated that the individual components employed can beseparately blended into the base fluid or can be blended therein invarious subcombinations, if desired. Ordinarily, the particular sequenceof such blending steps is not crucial. Moreover, such components can beblended in the form of separate solutions in a diluent. It ispreferable, however, to blend the additive components used in the formof a concentrate, as this simplifies the blending operations, reducesthe likelihood of blending errors, and takes advantage of thecompatibility and solubility characteristics afforded by the overallconcentrate.

Additive concentrates can thus be formulated to contain all of theadditive components and if desired, some of the base oil component, inamounts proportioned to yield finished fluid blends consistent with theconcentrations described above. In most cases, the additive concentratewill contain one or more diluents such as light mineral oils, tofacilitate handling and blending of the concentrate. Thus concentratescontaining up to about 50 wt % of one or more diluents or solvents canbe used, provided the solvents are not present in amounts that interferewith the low and high temperature and flash point characteristics andthe performance of the finished power transmission fluid composition. Inthis regard, the additive components used pursuant to this invention maybe selected and proportioned such that an additive concentrate orpackage formulated from such components will have a flash point of about170° C. or above, using the ASTM D-92 test procedure.

Power transmission fluids of the embodiments herein, as formulated asdescribed above, also generally provide enhanced extreme pressureproperties for applications where metal-to-metal contact is made underhigh pressures, e.g., pressures in excess of 2 GPa. Such fluids aresuitable for automatic and manual transmissions such as step automatictransmissions, continuously variable transmissions, automated manualtransmissions, and dual clutch transmissions. High metal-to-metalcontact pressures such as those found in automotive transmissions, forexample, may cause damage to transmission parts if a lubricant is usedthat does not possess sufficient extreme pressure protectioncharacteristics. However, power transmission fluid compositions asdescribed herein also have good extreme pressure performancecharacteristics.

The fluid compositions of embodiments of this invention described hereinmay be advantageously used in a wide variety of applications, including,for example, in automatic transmission fluids, manual transmissionfluids, fluids used in dual clutch transmissions, fluids used in heavyduty transmissions, fluids used in continuously variable transmissions,and gear lubricants. Further, the automatic transmission fluid may besuitable for use in at least one transmission with a slipping torqueconverter clutch, a lock-up torque converter clutch, a starting clutch,electronically controlled converter clutch, and/or one or more shiftingclutches, and so forth. Such transmissions may include four-, five-,six-, and seven-speed or more transmissions, and continuously variabletransmissions of the chain, belt, disk, or toroidal type. The clutchused with these fluids may comprise, e.g., the same clutch materials asdescribed indicated above. They also may be used in gear applications,such as industrial gear applications and automotive gear applications.Gear-types may include, but are not limited to, spur, spiral bevel,helical, planetary, and hypoid. They may be used in axles, transfercases, and the like. Further, they may also be useful in metal workingapplications.

EXAMPLES

Illustrative compositions suitable for use in the practice of thisinvention are presented in the following Examples, wherein all parts andpercentages are by weight unless specified otherwise.

Example 1 Squawk Pressure Studies

Component effects of automatic transmission fluids were evaluated ineight fluid samples, designated ATF-A through ATF-H (see Table 1 below).The test fluids had a baseline composition corresponding to thepreferred formulation described above in Table D with the followingmodifications. Six design variables, designated I-VI, which correspondedto six of the components identified in Table D, were applied, where “+”means the variable was present in the highest level of the correspondingrange described in Table D and “−” indicates its absence or presence atthe lowest level of the corresponding range described in Table D from agiven sample run, with the further qualification that “+” under DesignVariable VI indicates the sulfur source was sulfurized transesterifiedtriglyceride while “−” indicated that it was a sulfurized ester. Designvariables I-VI corresponded to the following six components of thebaseline fluid: I: Component (D); II: Component (B); III: Component (C);IV: Component (A); V: Rust Inhibitors: and VI: Sulfur Source.

Friction characteristics for the matrix of fluids were investigated on aLow Speed SAE#2 machine. Tests were conducted with cellulose paper basedfriction material lined plates, commercially obtained as BW 4329 platesfrom Borg Warner Automotive. Friction was measured and recorded at 40°C. and 120° C. at four different pressures: 0.40, 0.79, 1.97 and 3.39N/mm². Squawk pressure was measured on a commercially-available ZF GKRig using a test procedure supplied by ZF with the apparatus. The squawkpressure results corresponding to the various tested sample fluids arealso reported in Table 1 below. TABLE 1 Squawk Design Variablespressure, Fluid I II III IV V VI N/mm² ATF-A + − + − + − 0.50 ATF-B− + + − − + 1.90 ATF-C + − − − − + 0.40 ATF-D + + + + + + 1.38 ATF-E −− + + − − 2.20 ATF-F + + − + − − 1.13 ATF-G − + − − + − 1.05 ATF-H − −− + + + 1.60

Using these fluid samples FIGS. 4-10 are plots of squawk pressure versus∂μ/∂T as measured sliding speeds at a pressure of 0.79 N/mm². FIG. 11 isa plot of R² (for correlation of ∂μ/∂T to squawk) versus rpm for thetest pressure condition of 0.79 N/mm². FIGS. 12-17 are plots of squawkpressure versus ∂μ/∂T as measured sliding speeds at a pressure of 3.40N/mm². FIGS. 18-19 show coefficient of friction μ results observed forthe eight test fluids at a pressure of 0.79 N/mm² at temperatures at 40°C. and 120° C., respectively. Temperatures for ∂μ/∂T were bulktemperatures at given pressure and rpm. For example, if μ (40° C.) was0.152 and μ (120° C.) was 0.148, then ∂μ/∂T equal(0.148-0.152)/(120-40)=0.00005. Values were multiplied by 10,000 forease of handling. FIG. 20 is a plot of coefficient of ∂μ/∂T versussliding speed at a pressure of 0.79 N/mm². FIGS. 21-28 are plots ofsquawk pressure versus ∂μ/∂P at a series of different test conditions(viz., rpm's, temperature, pressure), as indicated therein. FIG. 29shows coefficient of friction μ results observed for test fluids attemperatures at 40° C. and 120° C., respectively.

The results indicate that squawk control improves with negative ∂μ/∂T.The results also show that merely providing a fluid having a positiveslope of μ-v is insufficient to improve squawk performance. Thecorrelation between squawk and ∂μ/∂T was only observed at specificconditions in the low speed rig, viz., at a pressure of 0.79 N/mm² andabove 50 rpm (0.27 m/s). The results also indicate that squawk controlimproves with negative ∂μ/∂P, albeit perhaps not as significantly as∂μ/∂T under the particular testing conditions applied in these studies.

The results also show that the presence or absence of certain individualcomponents, viz., Components (A)-(D), in the additive can significantlyinfluence variation in friction level due to change in temperature. Theresults indicated that four out of the six variables strongly influence∂μ/∂T (and ∂μ/∂P), which are Components (A)-(D) described herein. Theseresults indicate that levels of these four components should balanced tointroduce a small negative ∂μ/∂T condition for improved squawkperformance. In general it was found that the noise phenomena decreaseswith decreasing quasi-static friction level. Higher quasi-staticfriction is generally desirable for higher torque transmission.

As used throughout the specification and claims, “a” and/or “an” mayrefer to one or more than one. Unless otherwise indicated, all numbersexpressing quantities of ingredients, properties such as molecularweight, percent, ratio, reaction conditions, and so forth used in thespecification and claims are to be understood as being modified in allinstances by the term “about.” Accordingly, unless indicated to thecontrary, the numerical parameters set forth in the specification andclaims are approximations that may vary depending upon the desiredproperties sought to be obtained by the present invention. At the veryleast, and not as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques. Notwithstandingthat the numerical ranges and parameters setting forth the broad scopeof the invention are approximations, the numerical values set forth inthe specific examples are reported as precisely as possible. Anynumerical value, however, inherently contains certain errors necessarilyresulting from the standard deviation found in their respective testingmeasurements.

At numerous places throughout this specification, reference has beenmade to a number of U.S. patents. All such cited documents are expresslyincorporated in full into this disclosure as if fully set forth herein.

Other embodiments of the present invention will be apparent to thoseskilled in the art from consideration of the specification, Figure andpractice of the invention disclosed herein. It is intended that thespecification and examples be considered as exemplary only, with a truescope and spirit of the invention being indicated by the followingclaims.

1. A fluid composition, comprising: (1) a major amount of a base oil,and (2) a minor amount of an additive composition comprising alkoxylatedamine, dihydrocarbyl phosphite, metallic detergent, and phosphorylatedsuccinimide, in respective amounts effective for providing a negative∂μ/∂T during engaging, slipping or modulating of a power transmissionfriction torque transfer apparatus lubricated therewith.
 2. The fluidcomposition of claim 1, comprising 0.002-0.5 wt % alkoxylated amine,0.001-0.5 wt % dihydrocarbyl phosphite, 0.01-1.0 wt % metallicdetergent, and 0.01-12 wt % phosphorylated succinimide.
 3. The fluidcomposition of claim 1, comprising 0.01-0.25 wt % alkoxylated amine,0.01-0.2 wt % dihydrocarbyl phosphite, 0.01-0.7 wt % metallic detergent,and 0.01-10 wt % phosphorylated succinimide.
 4. The fluid composition ofclaim 1, wherein the additive composition is present in an amount ofabout 3 wt % to about 20 wt %, based on the fluid composition.
 5. Thefluid composition of claim 1, wherein the additive composition ispresent in an amount of about 5 wt % to about 15 wt %, based on thefluid composition.
 6. The fluid composition of claim 1, wherein thefluid composition is formulated such that the fluid compositioncomprises a viscosity at 100° C. of <6 cSt, a viscosity at 40° C. of <30cSt, and a Brookfield Viscosity at −40° C. of <10,000 cP, and whereinthe ∂μ/∂T slope value is determined from coefficient of friction andtemperature measurements taken on an SAE #2 Machine.
 7. The fluidcomposition of claim 1, wherein the base oil comprises one or more of anatural oil, a mixture of natural oils, a synthetic oil, a mixture ofsynthetic oils, a mixture of natural and synthetic oils, and a base oilderived from a Fischer-Tropsch or gas-to-liquid process.
 8. The fluidcomposition of claim 1, wherein the additive composition furthercomprises one or more of a additional friction modifier, an additionaldetergent, an additional dispersant, an antioxidant, an antiwear agent,an antifoam agent, a viscosity index improver, a copper corrosioninhibitor, an anti-rust additive, a seal swell agent, a metaldeactivator, and an air expulsion additive.
 9. An additive compositioncomprising alkoxylated amine, dihydrocarbyl phosphite, metallicdetergent, and phosphorylated succinimide, in respective amountseffective for providing a negative ∂μ/∂T during engagement of a powertransmission shifting clutch lubricated therewith.
 10. A method ofreducing NVH in a power transmission apparatus having a friction torquetransfer apparatus comprising lubricating the friction torque transferapparatus with a fluid composition that provides a negative ∂μ/∂T duringengaging, slipping or modulating the friction torque transfer apparatus,said fluid comprising alkoxylated amine, dihydrocarbyl phosphite,metallic detergent, and phosphorylated succinimide, in respectiveamounts effective therefor.
 11. A method for improving anti-NVH controlperformance in a power transmitting apparatus comprising: A) adding afluid to a power transmitting apparatus, said fluid comprising (i) abase oil, and (ii) an additive package comprising alkoxylated amine,dihydrocarbyl phosphite, metallic detergent, and phosphorylatedsuccinimide; and B) operating the fluid in the power transmittingapparatus, wherein the additive package being present in an amounteffective for providing a negative ∂μ/∂T during engaging, slipping ormodulating of a power transmission friction torque transfer apparatuslubricated therewith.
 12. The method of claim 11, wherein the frictiontorque transfer apparatus is selected from the group consisting of ashifting clutch, a starting clutch, a torque converter clutch, a bandclutch, disk or plate clutch, and a limited slip differential clutch.13. The method of claim 11, wherein the friction torque transferapparatus comprises a shifting clutch.
 14. The method of claim 11,wherein the fluid composition is formulated such that the fluidcomposition comprises a viscosity at 100° C. of <6 cSt, a viscosity at40° C. of <30 cSt, and a Brookfield Viscosity at −40° C. of <10,000 cP,and wherein the ∂μ/∂T slope value is determined from coefficient offriction and temperature measurements taken on an SAE #2 Machine.
 15. Amethod of reducing NVH in a power transmission apparatus having afriction torque transfer apparatus comprising lubricating the frictiontorque transfer apparatus with a fluid composition that provides anegative ∂μ/∂P during engaging, slipping or modulating the frictiontorque transfer apparatus, said fluid comprising alkoxylated amine,dihydrocarbyl phosphite, metallic detergent, and phosphorylatedsuccinimide, in respective amounts effective therefor.
 16. Atransmission containing the fluid composition of claim
 1. 17. Thetransmission of claim 16, wherein the transmission comprises acontinuously variable transmission.
 18. The transmission of claim 16,wherein the transmission comprises a dual clutch transmission.
 19. Thetransmission of claim 16, wherein the transmission comprises anautomatic transmission.
 20. The transmission of claim 16, wherein thetransmission comprises a manual transmission.
 21. The transmission ofclaim 16, wherein the transmission comprises one or more of anelectronically controlled converter clutch, a slipping torque converter,a lock-up torque converter, a starting clutch, and one or more shiftingclutches.
 22. The transmission of claim 16, wherein the transmissioncomprises a belt, chain, or disk-type continuously variabletransmission, a 4-speed or more automatic transmission, a manualtransmission, an automated manual transmission, or a dual clutchtransmission.
 23. A vehicle comprising an engine and a transmission, thetransmission including the fluid composition of claim 1.